Scientific Data Documentation
Access To Care File, 1996
DSN: CC37.NHIS96.ACCESSX
1996 National Health Interview Survey (NHIS)
Access to Care Final Public Use Data File
1. The 1996 National Health Interview Survey (NHIS) Access data
file contains a variety of data items addressing access to
health care services. These data items are identical to the
1995 Access data items.
As a result of a Federal government furlough, two weeks of
data collection were omitted in January of 1996. In addition,
in order to test the changing NHIS core questionnaire, for
much of the year the sample was split between the old (paper)
and the new (computerized) versions of the core questionnaire.
This data file includes only data obtained from the paper
version of the NHIS questionnaire. The sample size is considerably
smaller than in the previous year (63,402 vs. 102,467).
The weights have been adjusted for these factors to produce
national estimates, however, there may be a minor seasonal
effect which is not corrected by the weighting.
2. The 1996 Access supplement was administered for the full year
(except as mentioned above) in all of the NHIS sample households
interviewed with the old paper core using three-quarters
of the sample households from January-June and one-half of the
sample households from July-December. Information was
collected from a household respondent about all family members
who participated in the NHIS.
The 1996 Access file is structured in the following way:
a. The NHIS person record from the core questionnaire
(locations 1-335)
b. The weight fields (locations 201-236)
c. Fields needed for calculating variances (locations
337-358)
d. Data from supplement (locations 401-439)
Note: All data from the Access supplement have been shifted to
start in location 401 in order to accommodate a longer public
use person record required by the new sample design in 1995.
3. In 1996, two types of item non-response were identified:
(1) "Not ascertained" (codes 8, 98, or 998) includes blanks
when there should have been a response or when an impos-
sible code appeared and;
(2) Responses of "don't know" or "refused" when the question
was asked (codes 9, 99 and 999).
4. The overall response rate for the 1996 Access was 90.0 per-
cent. This response rate was calculated as follows:
Household response rate from core of 93.8 percent multiplied
by 95.9 percent who responded to the Access section yields
an overall response rate of 90.0 percent.
Dummy records were created for those with no response to the
entire section (see file location 400).
5. Weights and variances:
Since the NHIS uses a multistage sample design to represent
the civilian non-institutionalized population of the United
States, weights must be used to make accurate estimates based
on data from the National Health Interview Survey.
A set of weights are included on the 1996 file:
The first weight listed below (i.e. the Final Basic Weight)
will be used in most analyses of the Access data.
The Final Basic Weight (location 219-227) is the equivalent of
the Annual Final Basic Weight found on the NHIS Person Record
of the Basic Health and Demographic component of the survey
(i.e. the Core questionnaire). A national estimate of all
person level variables can be made using this weight.
This weight will be used in conjunction with Access data items
in file locations 401-439.
The Final Quarter Basic Weight before age-sex-race/ethnicity
adjustment (loc. 172-177) is required by some software packages
for variance estimation for surveys with complex sample
designs. This weight is also included on the file.
As mentioned above, the sample design for the NHIS was changed
for 1995. Data from 1995 and 1996 can be combined with data
from previous years, however, variances for 1995 and 1996
must be calculated separately from variances of previous
years. In addition, because of the smaller sample size in
1996, some of the design elements were combined for reasons of
confidentiality. The exact changes are included in the explanation
below.
There are a number of computer programs that yield variance
estimates for data based on complex sample surveys. Some are
based on replication approaches and others are based on Taylor
linearization approaches. In addition to the Final Quarter
Basic Weight before age-sex-race/ethnicity adjustment (which is
the weight prior to post-stratification), included on the
Access file is the substratum for variance estimation (loc.
342-343), the secondary sampling unit (loc. 344-350), Panel 4
(loc. 352), the variance PSU for 1996 (loc. 358), the
collapsed variance stratum for 1996 (loc. 354-357), and the
NSR Status variable for 1996 (loc. 353) to permit the analyst
the capability of using such variance estimation procedures.
These variables and weights are necessary for directly
calculating sampling variances.
6. Estimating annual numbers of events or conditions
a. To reduce respondent error, the recall period for
questions about some events is limited to two weeks.
These events are: bed days and other restricted activity
days, work loss and school loss days, and doctor visits.
The two-week variables are found in locations 98-107 and
120-121. Estimates of the total number of occurrences of
these events in the population can be derived as follows:
Number of events x 26 (number of two-week
periods in a year) x Final Basic Weight
= Total number of events occurring in the
population during the annual period,
i.e. 1996.
Example: Number of bed days (Loc. 100-101) x 26 x Final
Basic Weight (Loc. 219-227) = total number of bed days
reported for the population in 1996.
b. The recall period for acute incidence conditions is also
two weeks and a national estimate of the total number of
acute incidence conditions is calculated using the same
procedures as for two-week events for the annual period.
Number of acute incidence conditions x 26 x Final
Basic Weight
= Total number of acute incidence conditions
occurring in the population during 1996.
Note: An acute incidence condition is an acute condition
with onset during the two weeks preceding the date of
interview.
c. The recall period for information on hospitalizations is
12 months. However, in calculating number of discharges
(Locations 132-133, 137-138), only discharges occurring
in the past 6 months are counted. Therefore, the
weighted estimates must be calculated as follows:
Number of discharges x 2 x Final Basic Weight
= Total number of discharges occurring in the
population in 1996.
7. Calculation of rates for events and conditions:
The number of events or conditions estimated for the
population, as described in item 6, above, can be used as the
basis for calculating rates of occurrence of these events (or
conditions) per person and per 100 persons for the total U.S.
population and for various population subgroups.
Note: Only rates can be estimated from these data. The
percent of the population experiencing a particular type of
event during the data year cannot be estimated. (The percent
of the population experiencing the event in the reporting
period (i.e. two weeks or 6 months) can be estimated but is
generally not meaningful.)
8. Data on hospital episodes and days, based on a 12-month recall
are in locations 122-131. The Final Basic Weight is used for
calculating estimates of these events in the same way it is
used for all other person-based variables. These variables do
permit estimating the percent of the population in this annual
period experiencing a hospital episode in the past year and
the percent of that population having a specified number of
hospital days.
9. Guidelines for Citation of Data
With the goal of mutual benefit, the National Center for
Health Statistics (NCHS) requests that recipients of data
files cooperate in certain actions related to their use.
Any published material derived from the data should
acknowledge NCHS as the original source. The suggested
citation to appear at the bottom of all tables is as follows:
Source: National Center for Health Statistics (1996)
When cited in a bibliography, the suggested citation should
read:
National Center for Health Statistics (1998). Data File
Documentation, National Health Interview Survey of Access
to Care, 1996 (machine readable data file and
documentation), National Center for Health Statistics,
Hyattsville, Maryland.
The published material should also include a disclaimer that
credits any analyses, interpretations, or conclusions reached
to the author (recipient of the data file) and not to NCHS,
which is responsible only for the initial data. Consumers who
wish to publish a technical description of the data should
make a reasonable effort to insure that the description is not
inconsistent with that published by NCHS.
AC-1
1996 NATIONAL HEALTH INTERVIEW SURVEY (NHIS)
ACCESS TO CARE PUBLIC USE FILE
Outline of Items and Codes
63,402 Records
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
1-2 - RECORD TYPE
63,402 70. Access to Care Supplement
______________________________________________________________________
3-4 HH-2 PROCESSING YEAR
63,402 96. 1996
______________________________________________________________________
5-14 Recode - HOUSEHOLD ID
______________________________________________________________________
15-16 - - PERSON NUMBER
______________________________________________________________________
17-18 - - BLANK (Record Serial Number on some
other record types)
______________________________________________________________________
19-20 - SAMPLING WEEK CODE
(Numbered within quarter)
3,680 01. Week 1
3,422 02. Week 2
5,414 03. Week 3
4,966 04. Week 4
5,009 05. Week 5
4,867 06. Week 6
5,512 07. Week 7
5,183 08. Week 8
5,390 09. Week 9
4,992 10. Week 10
4,714 11. Week 11
5,128 12. Week 12
5,125 13. Week 13
______________________________________________________________________
AC-2
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
21 Recode LATE INTERVIEW (OR LAST ATTEMPT)
FLAG
36,891 0. Interview not late
18,591 1. One week late
6,372 2. Two weeks late
1,548 3. Unknown
______________________________________________________________________
22-23 HH-11c,d TYPE OF LIVING QUARTERS:
Housing Unit = (00-07)
1,234 00. Housing unit; kind unknown
58,363 01. House, apartment, flat
37 02. HU in nontransient hotel,
motel, etc.
5 03. HU-permanent in transient
hotel, motel, etc.
20 04. HU in rooming house
3,072 05. Mobile home or trailer with
no permanent room added
450 06. Mobile home or trailer with one
or more permanent rooms added
51 07. HU not specified above
Other Unit = (08-13)
39 08. Quarters not HU in rooming or
boarding house
3 09. Unit not permanent in transient
hotel, motel, etc.
14 10. Unoccupied site for mobile
home, trailer, or tent
90 11. Student quarters in college
dormitory
24 12. Other unit not specified above
0 13. Other unit; kind unknown
______________________________________________________________________
24 HH-12a HAS TELEPHONE
57,080 1. Yes, phone number given
2,558 2. Yes, no phone number given
3,099 3. No
665 4. Unknown
______________________________________________________________________
25 A-1 SEX
30,358 1. Male
33,044 2. Female
______________________________________________________________________
AC-3
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
26 - AGE IMPUTED FLAG
63,400 0. Age known
2 1. Age unknown, imputed
as 34
______________________________________________________________________
27-28 Person AGE
Column
976 00. Under 1 year
62,241 01-89. Number of years
185 90. 90+ years old
______________________________________________________________________
29 Recode AGE RECODE #1
4,918 1. Under 5 years
13,210 2. 5-17 years
5,568 3. 18-24 years
19,974 4. 25-44 years
12,598 5. 45-64 years
2,213 6. 65-69 years
1,928 7. 70-74 years
2,993 8. 75 years and over
______________________________________________________________________
30 Recode AGE RECODE #2
6,008 1. Under 6 years
11,219 2. 6-16 years
6,469 3. 17-24 years
9,603 4. 25-34 years
10,371 5. 35-44 years
7,673 6. 45-54 years
4,925 7. 55-64 years
4,141 8. 65-74 years
2,993 9. 75 years and over
______________________________________________________________________
31-32 Recode AGE RECODE #3
2,905 00-35. Months
60,497 36. Over 3 years old
______________________________________________________________________
33 - MONTH OF BIRTH IMPUTED FLAG
60,272 0. Month known
3,090 1. Month unknown, '8' imputed
40 9. Date of birth unknown
______________________________________________________________________
AC-4
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
34-39 A-3 - MONTH AND YEAR OF BIRTH
34-35 Month
01. January 08. August
02. February 09. September
03. March 10. October
04. April 11. November
05. May 12. December
06. June 99. Unknown
07. July
36-39 Year of Birth
168 1905. 1905 and before
63,194 1906-1997. 1906-1997
40 9999. Unknown
______________________________________________________________________
40 Recode HISPANIC ORIGIN IMPUTED FLAG
62,712 0. Hispanic origin known
690 1. Hispanic origin imputed from
reference person
______________________________________________________________________
41-42 A-6 MAIN RACIAL BACKGROUND* - Reported
(see notation for locations 43-45)
46,996 01. White
9,027 02. Black/African American**
482 03. Indian (American)
325 06. Chinese
455 07. Filipino
987 15. Other API (includes Hawaiian,
Korean, Vietnamese, Japanese,
Asian Indian, Samoan, and
Guamanian)
3,797 16. Other race (includes Eskimo
and Aleut)
181 17. Multiple race
1,152 99. Unknown
_____________________________________________________________________
* Some categories may be too small to analyze separately and
therefore may produce unreliable estimates; in addition, counts
may not agree with those produced by the Census Bureau.
** For convenience, the category 'Black/African American' will be shown
as 'Black' in all observed race or race recode locations throughout
the documentation.
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
43-45 Recode RACE RECODES
43 Recode 1* Persons whose Main
51,962 1. White Racial Background
9,065 2. Black (location 41-42) was
2,375 3. Other "other" or "unknown"
were classified in
44 Recode 2 the following recodes
by using the racial
51,962 1. White background observed
11,440 2. Non-white by the interviewer.
Use of these recodes
45 Recode 3 is recommended for
estimating statistics
9,065 1. Black for the groups shown
54,337 2. Non-black here.
______________________________________________________________________
46-47 A-5 HISPANIC ORIGIN**
12 00. Multiple Hispanic
1,387 01. Puerto Rican
646 02. Cuban
3,935 03. Mexican-Mexicano
4,391 04. Mexican-American
99 05. Chicano
1,133 06. Other Latin American
1,184 07. Other Spanish
338 08. Spanish, DK type
114 09. Unknown if Spanish origin
50,163 10. Not Spanish origin
______________________________________________________________________
48 L-7 MARITAL STATUS
14,293 0. Under 14 years old
28,314 1. Married - spouse in household
494 2. Married - spouse not in household
3,022 3. Widowed
3,475 4. Divorced
1,102 5. Separated
12,070 6. Never married
632 7. Unknown
______________________________________________________________________
*This recode is used to define race in the Current Estimates tables.
**If unknown, the family reference person code was imputed. A flag
indicating imputation is in loc. 40 and the relationship to reference
person is in loc. 63.
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
49 L-1 VETERAN STATUS
38,331 1. Non-veteran
1,311 2. WW I and WW II
800 3. Korean War
1,715 4. Vietnam veteran
810 5. Post-Vietnam
1,070 6. Other service
163 7. Served in Armed Forces,
unknown if war veteran
1,074 8. Unknown if served in
Armed Forces
18,128 Blank. Under 18 years old
______________________________________________________________________
50 L-1 ACTIVE GUARD/RESERVE STATUS FOR
PERSONS ON ACTIVE DUTY IN ARMED
FORCES
38,331 0. Non-veteran
363 1. All service in Guard/Reserve
740 2. Some service in Guard/Reserve
36 3. Unknown if all service in
Guard/Reserve
4,159 4. No active service in Guard/
Reserve
1,645 5. Unknown if ever active member
in Guard/Reserve or served
in Armed Forces
18,128 Blank. Under 18 years old
______________________________________________________________________
51-52 L-2 EDUCATION OF INDIVIDUAL - COMPLETED YEARS
2,628 00. Never attended; kindergarten
only
19,974 01-11. Grades 1-11
16,207 12. Grade 12
College:
3,321 13. 1 year
4,433 14. 2 years
1,602 15. 3 years
5,424 16. 4 years
1,039 17. 5 years
2,762 18. 6 years or more
1,094 19. Unknown
4,918 Blank. Under 5 years old
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
53 Recode EDUCATION OF INDIVIDUAL
2,628 0. None; kindergarten only
12,480 1. 1-8 years (elementary)
7,494 2. 9-11 years (high school)
16,207 3. 12 years (high school
graduate)
9,356 4. 1-3 years (college)
5,424 5. 4 years (college graduate)
3,801 6. 5+ years (post-college)
1,094 7. Unknown
4,918 Blank. Under 5 years old
______________________________________________________________________
54-55 - HIGHEST EDUCATION OF RESPONSIBLE
ADULT FAMILY MEMBER (Detail)
151 00. Never attended; kindergarten
only
9,278 01-11. Grades 1-11
20,685 12. Grade 12
College:
4,719 13. 1 year
7,364 14. 2 years
2,688 15. 3 years
9,589 16. 4 years
2,073 17. 5 years
6,048 18. 6 years or more
807 19. Unknown
______________________________________________________________________
56 Recode HIGHEST EDUCATION OF RESPONSIBLE
ADULT FAMILY MEMBER
151 0. None; kindergarten only
3,807 1. 1-8 years (elementary)
5,471 2. 9-11 years (high school)
20,685 3. 12 years (high school
graduate)
14,771 4. 1-3 years (college)
9,589 5. 4 years (college graduate)
8,121 6. 5+ years (post-college)
807 7. Unknown
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
57 L-8 FAMILY INCOME $20,000 OR LESS
18,637 1. Less than $20,000
42,177 2. $20,000 or more
2,588 3. Unknown
______________________________________________________________________
58-59 L-8 FAMILY INCOME
243 00. Less than $1,000
366 01. $ 1,000 - $1,999
319 02. 2,000 - 2,999
356 03. 3,000 - 3,999
433 04. 4,000 - 4,999
694 05. 5,000 - 5,999
695 06. 6,000 - 6,999
699 07. 7,000 - 7,999
701 08. 8,000 - 8,999
941 09. 9,000 - 9,999
1,132 10. 10,000 - 10,999
705 11. 11,000 - 11,999
1,304 12. 12,000 - 12,999
838 13. 13,000 - 13,999
828 14. 14,000 - 14,999
1,100 15. 15,000 - 15,999
777 16. 16,000 - 16,999
810 17. 17,000 - 17,999
1,042 18. 18,000 - 18,999
1,216 19. 19,000 - 19,999
4,786 20. 20,000 - 24,999
4,130 21. 25,000 - 29,999
4,150 22. 30,000 - 34,999
3,179 23. 35,000 - 39,999
3,180 24. 40,000 - 44,999
2,824 25. 45,000 - 49,999
15,137 26. $50,000 and over
10,817 27. Unknown
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
60 Recode FAMILY INCOME
1,717 0. Under $5,000
1,389 1. $ 5,000 - $ 6,999
2,341 2. 7,000 - 9,999
4,807 3. 10,000 - 14,999
4,945 4. 15,000 - 19,999
4,786 5. 20,000 - 24,999
8,280 6. 25,000 - 34,999
9,183 7. 35,000 - 49,999
15,137 8. $50,000 or more
10,817 9. Unknown
______________________________________________________________________
61 Generated NHIS POVERTY INDEX*
48,720 1. At or above poverty threshold
8,572 2. Below poverty threshold
6,110 3. Unknown
______________________________________________________________________
62-63 FAMILY RELATIONSHIP
62 A-2 Type of Family
6,440 &. Primary individual
684 -. Secondary individual
56,152 0. Primary family
126 1-9. Secondary family
63 A-2 Relationship to Reference Person
6,048 &. Reference person, living alone
18,770 0. Reference person, 2+ persons
in household
13,756 1. Spouse, other spouse NOT in
Armed Forces and living at home
151 2. Spouse, other spouse IN Armed
Forces and living at home
21,000 3. Child of reference person or
spouse
1,252 4. Grandchild of reference person
or spouse
645 5. Parent of reference person or
spouse
1,763 6. Other relative
17 7. Child of military family with
no eligible reference person
0 9. DK or refused
______________________________________________________________________
*Based on family size, number of children under 18 years old and
family income using the 1995 poverty levels derived from the August,
1996 Current Population Survey.
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
64 Recode FAMILY RELATIONSHIP
6,048 1. Living alone
1,076 2. Living only with non-relative
28,297 3. Living with spouse
27,981 4. Living with relative - other
______________________________________________________________________
65-66 Generated - SIZE OF FAMILY*
Unrelated individuals are coded 01
______________________________________________________________________
67 Generated SIZE OF FAMILY RECODE
62,665 1-8. Number of members
737 9. 9+ members
______________________________________________________________________
68 A-2 PARENT/OTHER ADULT RELATIVE (under 25
years old and never married)
13,233 1. Both parents, no other relative
3,521 2. Mother only
324 3. Father only
1,835 4. Both parents and other 21+
year old adult relative
1,271 5. Mother and other 21+ year old
adult relative
152 6. Father and other 21+ year old
adult relative
281 7. No parent, but one 21+ year
old adult relative
427 8. No parent, but two or more 21+
year old adult relatives
164 9. Unknown
849 0. Other
41,345 Blank. Not applicable (25+ years old
or ever married)
______________________________________________________________________
*Count includes spouse in military but living at home.
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
69 B-1 MAJOR ACTIVITY (18+ years old)
B-8
28,283 1. Working
7,516 2. Keeping house
2,504 3. Going to school
6,513 4. Something else
458 5. Unknown
18,128 Blank. Not applicable (under 18
years old)
______________________________________________________________________
70 G-4 HEALTH STATUS
22,720 1. Excellent
18,116 2. Very Good
15,237 3. Good
4,899 4. Fair
1,697 5. Poor
733 6. Unknown
______________________________________________________________________
71 Recode ACTIVITY LIMITATION STATUS*- (all ages)
3,018 1. Unable to perform major activity
3,343 2. Limited in kind/amount major
activity
2,727 3. Limited in other activities
54,314 4. Not limited (includes unknowns)
______________________________________________________________________
72 Recode ACTIVITY LIMITATION STATUS MEASURED BY
"ABILITY TO WORK" (18-69 years old)
2,829 1. Unable to work
1,765 2. Limited in kind/amount of work
1,490 3. Limited in other activities
34,269 4. Not limited (includes unknowns)
23,049 Blank. Not applicable (under 18
years old, 70+ years old)
______________________________________________________________________
*This location is used to categorize persons with limitation of
activity in the Current Estimates tables.
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
73 B-11 LIMITATION OF SCHOOL ACTIVITIES
(5-17 years old)
81 1. Unable to attend school
438 2. Attends special school/classes
74 3. Needs special school/classes
124 4. Limited in school attendance
282 5. Limited in other activities
12,211 6. Not limited (includes unknowns)
50,192 Blank. Not applicable (under 5 years
old or 18+ years old)
______________________________________________________________________
74 B-14 NEEDS HELP WITH PERSONAL CARE
(5-59 years old and limited,
or 60-69 years old)
408 1. Unable to perform personal
care needs
822 2. Limited in performing other
routine needs
8,488 3. Not limited in performing
personal or routine needs
404 4. Unknown
53,280 Blank. Not applicable (under 5
years old; 5-59 years old
not limited; 70+ years old)
_________________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
75 D-1 EMPLOYMENT STATUS IN PAST 2 WEEKS
(18+ years old)
In the Labor Force: (1-7)
Currently employed: (1-3)
28,767 1. Worked in past 2 weeks
494 2. Did not work, has job; not
on lay-off and not looking
for work
28 3. Did not work, has job;
looking for work
Unemployed: (4-7)
93 4. Did not work, has job; on
lay-off
6 5. Did not work, has job; on
lay-off and looking for work
200 6. Did not work, has job; unknown
if looking or on lay-off
960 7. Did not work, has no job;
looking for work or on lay-off
14,726 8. Not in Labor Force (18+ years old)
18,128 Blank. Not applicable (under 18 years
old)
_________________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
76 L-6 CLASS OF WORKER
14,726 0. Not in labor force
21,596 1. Private company
756 2. Federal Government employee
1,388 3. State Government employee
2,369 4. Local Government employee
789 5. Incorporated business
2,615 6. Self-employed
29 7. Without pay
35 8. Never worked
971 9. Unknown
18,128 Blank. Under 18 years old
_________________________________________________________________________
77-79 - BLANK
_________________________________________________________________________
80-81 Recode - INDUSTRY RECODE 1
SEE APPENDIX B
_________________________________________________________________________
82-83 Recode - INDUSTRY RECODE 2
SEE APPENDIX B
_________________________________________________________________________
84-86 - BLANK
_________________________________________________________________________
87-88 Recode - OCCUPATION RECODE 1
SEE APPENDIX C
_________________________________________________________________________
89-90 Recode - OCCUPATION RECODE 2
SEE APPENDIX C
_________________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
91 L-R RESPONDENT FOR CORE QUESTIONS
27,761 1. Self (entirely)
3,242 2. Self (partly)
31,712 3. Proxy
687 4. Unknown
________________________________________________________________________
92 Recode CONDITION LIST ASSIGNED AND ASKED
10,548 1. Condition List 1, Skin and
musculoskeletal
10,568 2. Condition List 2, Impairments
10,388 3. Condition List 3, Digestive
10,472 4. Condition List 4, Miscellaneous
10,113 5. Condition List 5, Circulatory
10,575 6. Condition List 6, Respiratory
738 7. Unknown
_________________________________________________________________________
93-94 G-5 HEIGHT WITHOUT SHOES (18+ years old)
363 58. 58 inches or less
43,782 59-76. Number of inches
246 77. 77 inches or more
883 99. Unknown
18,128 Blank. Under 18 years old
_________________________________________________________________________
95-97 G-5 WEIGHT WITHOUT SHOES (18+ years old)
288 097. 97 pounds or less
42,919 098-289. Number of pounds
320 290. 290 pounds or more
1,747 999. Unknown
18,128 Blank. Under 18 years old
_________________________________________________________________________
98-99 Recode TOTAL RESTRICTED ACTIVITY DAYS IN
PAST TWO WEEKS
57,092 00. None
6,310 01-14. Days
_________________________________________________________________________
100-101 D-4 BED DAYS IN PAST TWO WEEKS
59,733 00. None
3,669 01-14. Days
_________________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
102-103 D-2 WORK-LOSS DAYS IN PAST TWO WEEKS
61,810 00. None
1,592 01-14. Days
_________________________________________________________________________
104-105 D-3 SCHOOL-LOSS DAYS IN PAST TWO WEEKS
62,431 00. None
971 01-14. Days
_________________________________________________________________________
106-107 D-6 OTHER DAYS OF RESTRICTED ACTIVITY
IN PAST TWO WEEKS
60,449 00. None
2,953 01-14. Days
_________________________________________________________________________
108-110 G-2 BED DAYS IN PAST 12 MONTHS
35,920 000. None
26,460 001-365. 1-365 days
1,022 366. Unknown
_________________________________________________________________________
111 Recode BED DAYS IN PAST 12 MONTHS
35,920 0. None
20,817 1. 1-7 days
4,084 2. 8-30 days
1,243 3. 31-180 days
316 4. 181-365 days
1,022 5. Unknown
_________________________________________________________________________
112-114 G-3 DOCTOR VISITS IN PAST 12 MONTHS
15,335 000. None
47,627 001-996. Visits
0 997. 997+ visits
440 998. Unknown
_________________________________________________________________________
115 G-3 INTERVAL SINCE LAST DOCTOR VISIT
182 0. Never
48,478 1. Less than 1 year
6,010 2. 1 to less than 2 years
4,842 3. 2 to less than 5 years
2,128 4. 5 years or more
1,762 5. Unknown
_________________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
116-117 Generated - NUMBER OF CONDITIONS
_________________________________________________________________________
118-119 Generated - NUMBER OF ACUTE INCIDENCE CONDITIONS
_________________________________________________________________________
120-121 Generated - NUMBER OF TWO-WEEK DOCTOR VISITS
_________________________________________________________________________
122-123 Generated - NUMBER OF SHORT-STAY HOSPITAL EPISODES
IN PAST 12 MONTHS
_________________________________________________________________________
124-126 Generated - SHORT-STAY HOSPITAL EPISODE DAYS IN
PAST 12 MONTHS
_________________________________________________________________________
127-128 Generated - NUMBER OF SHORT-STAY HOSPITAL EPISODES
IN PAST 12 MONTHS EXCLUDING DELIVERY*
_________________________________________________________________________
129-131 Generated - SHORT-STAY HOSPITAL EPISODE DAYS IN
PAST 12 MONTHS EXCLUDING DELIVERY*
_________________________________________________________________________
132-133 Generated - NUMBER OF SHORT-STAY HOSPITAL DISCHARGES
IN PAST 6 MONTHS
_________________________________________________________________________
134-136 Generated - NUMBER OF DAYS IN SHORT-STAY HOSPITAL
IN PAST 12 MONTHS FOR DISCHARGES IN
PAST 6 MONTHS
_________________________________________________________________________
137-138 Generated - NUMBER OF SHORT-STAY HOSPITAL DISCHARGES
IN PAST 6 MONTHS EXCLUDING DELIVERY*
_________________________________________________________________________
139-141 Generated - NUMBER OF DAYS IN SHORT-STAY HOSPITAL
IN PAST 12 MONTHS FOR DISCHARGES IN
PAST 6 MONTHS EXCLUDING DELIVERY*
_________________________________________________________________________
*Based on operation codes and reason entered hospital
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
142-143 - BLANK
_________________________________________________________________________
144 L-9b YEARS LIVED IN STATE OF PRESENT
RESIDENCE
1,766 1. Less than 1 year
5,762 2. 1 yr., less than 5 yrs.
6,429 3. 5 yrs., less than 10 yrs.
5,243 4. 10 yrs., less than 15 yrs.
32,468 5. 15 years or more
3,051 9. DK refused
8,683 Blank. Not applicable (foreign
born)
_________________________________________________________________________
145 L-9c YEARS LIVED IN UNITED STATES
274 1. Less than 1 year
1,339 2. 1 yr., less than 5 yrs.
1,667 3. 5 yrs., less than 10 yrs.
1,144 4. 10 yrs., less than 15 yrs.
3,997 5. 15 years or more
262 9. DK refused
54,719 Blank. Not applicable (U.S. born)
_________________________________________________________________________
146-171 - - BLANK
_________________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
172-177 - - FINAL QUARTER BASIC WEIGHT BEFORE
AGE-SEX-RACE/ETHNICITY ADJUSTMENT
(has one implied decimal)
_________________________________________________________________________
178 SAMPLING QUARTER
16,902 1. Quarter 1
19,814 2. Quarter 2
13,470 3. Quarter 3
13,216 4. Quarter 4
______________________________________________________________________
179-181 - - BLANK
______________________________________________________________________
182 Unit Control REGION
File
12,500 1. Northeast
13,606 2. Midwest
21,982 3. South
15,314 4. West
______________________________________________________________________
183 Unit Control GEOGRAPHIC DISTRIBUTION
File
MSA Size
8,007 1. 5,000,000 or more
7,914 2. 2,500,000 - 4,999,999
15,124 3. 1,000,000 - 2,499,999
6,747 4. 500,000 - 999,999
7,811 5. 250,000 - 499,999
4,520 6. 100,000 - 249,999
810 7. Under 100,000
12,469 Blank. Non-MSA
______________________________________________________________________
184-185 - - BLANK
______________________________________________________________________
186 Unit Control MSA - NON-MSA RESIDENCE
File
20,826 1. In MSA; in Central City
30,107 2. In MSA; not in Central City
12,469 3. Not in MSA
______________________________________________________________________
187-189 - - BLANK
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
190-200 - - CHRONIC CONDITION PREVALENCE AND
INCIDENCE FACTOR (XX.XXXXXXXXX) -
character format with implied
decimal
_________________________________________________________________________
FINAL BASIC WEIGHT
201-209 - - QUARTER
210-218 - - SEMI-ANNUAL (QUARTER/2)
219-227 - - ANNUAL (QUARTER/4)
_________________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
_______________________________________________________________________
6.5 WEIGHT
228-236 - - QUARTER, SEMI-ANNUAL AND ANNUAL*
_________________________________________________________________________
ESTIMATED RESTRICTED ACTIVITY DAYS
IN PAST 2 WEEKS
237-245 - - QUARTER, SEMI-ANNUAL AND ANNUAL*
_________________________________________________________________________
ESTIMATED BED DAYS IN PAST 2 WEEKS
246-254 - - QUARTER, SEMI-ANNUAL AND ANNUAL*
_________________________________________________________________________
ESTIMATED WORK-LOSS DAYS IN PAST
2 WEEKS
255-263 - - QUARTER, SEMI-ANNUAL AND ANNUAL*
_________________________________________________________________________
ESTIMATED SCHOOL-LOSS DAYS IN PAST
2 WEEKS
264-272 - - QUARTER, SEMI-ANNUAL AND ANNUAL*
_________________________________________________________________________
ESTIMATED DOCTOR VISITS IN PAST
12 MONTHS
273-281 - - QUARTER
282-290 - - SEMI-ANNUAL
291-299 - - ANNUAL
_________________________________________________________________________
ESTIMATED SHORT-STAY HOSPITAL EPISODE
DAYS IN PAST 12 MONTHS
300-308 - - QUARTER
309-317 - - SEMI-ANNUAL
318-326 - - ANNUAL
_________________________________________________________________________
327-335 - - ANNUAL ESTIMATED NUMBER OF SHORT-STAY
HOSPITAL EPISODES IN PAST 12 MONTHS
_________________________________________________________________________
* Estimates can be made for these periods depending on whether one
quarter, two quarters or all four quarters of records are used.
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
336 - - BLANK
______________________________________________________________________
337-340 Recode - STRATUM FOR VARIANCE ESTIMATION
______________________________________________________________________
341 Recode - PSU FOR VARIANCE ESTIMATION
______________________________________________________________________
342-343 Recode - SUBSTRATUM FOR VARIANCE ESTIMATION
______________________________________________________________________
344-350 Generated - SECONDARY SAMPLING UNIT
______________________________________________________________________
351 Unit Control TYPE OF PSU
File
41,421 1. Self representing
21,981 2. Non self representing
______________________________________________________________________
352 Unit Control PANEL 4
File
63,402 1-4. Code used to identify
nationally representative
subsamples
______________________________________________________________________
353 - NSR STATUS VARIABLE
______________________________________________________________________
354-357 - COLLAPSED VARIANCE STRATUM
______________________________________________________________________
358 - VARIANCE PSU
______________________________________________________________________
359-399 - - BLANK
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
400 Recode DUMMY RECORD FLAG
2,586 1. Dummy record for locations
401-440
60,816 Blank. Not a dummy record
______________________________________________________________________
401 1a IS THERE USUAL PERSON/
PLACE FOR MEDICAL CARE
52,922 1. Yes
7,353 2. No
186 3. More than one
2,722 8. Not ascertained
219 9. DK or refused
______________________________________________________________________
402 1b ONE PLACE MOST OFTEN
(Has more than one usual
person or place Q 1a = 3)
127 1. Yes
47 2. No
10 8. Not ascertained
2 9. DK or refused
63,216 Blank. NA
______________________________________________________________________
403-404 2 MAIN REASON NO USUAL SOURCE
289 01. Two or more usual
doctors/places
3,377 02. Doesn't need doctor
244 03. Doesn't like/trust/
believe in doctors
140 04. Doesn't know where to go
469 05. Previous doctor not
available/moved
1,689 06. No insurance/can't
afford it
6 07. Speaks different language
32 08. No care available/
not convenient
512 09. Changed residence
327 10. Other reason
261 98. Not ascertained
66 99. DK or refused
55,990 Blank. NA - Has/don't know if has
one usual source of care
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
405 3a ONE PLACE MOST OFTEN
(Q 1a = 2 and Q 2 = 01)
97 1. Yes
74 2. No
68 8. Not ascertained
3 9. DK or refused
63,160 Blank. NA
______________________________________________________________________
406 3b PLACE FOR PREVENTIVE CARE
(Q 1a = 2 and Q 2 = 01 and Q 3a
NE 1)
81 1. Yes
84 2. No
22 3. Not ascertained
5 4. DK or refused
63,210 Blank. NA
______________________________________________________________________
407 4a GO ANY PLACE IN PAST 12
MONTHS FOR MEDICAL CARE
2,728 1. Yes
4,464 2. No
2,912 8. Not ascertained
152 9. DK or refused
53,146 Blank. NA - Has a usual source
of care
______________________________________________________________________
408-409 4b KIND OF PLACE
355 01. Hospital emergency room
210 02. Urgent care/walk-in clinic
1,118 03. Doctor's office
479 04. Clinic
164 05. Health center
139 06. Hospital outpatient clinic
84 07. HMO/Prepaid group
39 08. Military or VA health
care facility
92 09. Some other place
23 98. Not ascertained
25 99. DK or refused
60,674 Blank. NA
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
410 4c WOULD STILL GO TO PLACE
(Does not have a usual source of care,
care but did go to a place for medical
care sometime in the past 12 months,
Q 4a = 1)
1,462 1. Yes
991 2. No
23 8. Not ascertained
252 9. DK or refused
60,674 Blank. NA
______________________________________________________________________
411-412 4d MAIN REASON WOULD NOT USE PLACE NOW
(Does not have a usual source of care
but did go to a place for medical care
sometime in the past 12 months and
would not use this place now Q 4c = 2)
410 01. Changed residence/moved
24 02. Changed jobs
30 03. Employer changed
insurance coverage
64 04. Former usual source
not available
5 05. Owed money to former source
76 06. Dissatisfied with
former source/like
new source better
148 07. Medical care needs changed
14 08. Former source stopped
taking insurance/coverage
199 09. Some other reason
13 98. Not ascertained
8 99. DK or refused
62,411 Blank. NA
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
413 Recode REGULAR SOURCE OF MEDICAL CARE
52,922 1. Single regular source
224 2. Multiple regular sources,
but sees one most often
204 3. Multiple regular sources,
but no one source seen
most often
2,524 4. No current regular source
but had a regular source
sometime in the past year
4,358 5. No current regular source
of care and none in past
year
229 6. No current regular source
and unknown if any in past
year
2,722 8. Not ascertained
219 9. DK or refused
______________________________________________________________________
414-415 5a KIND OF PLACE
759 01. Hospital emergency room
712 02. Urgent care/walk-in clinic
35,675 03. Doctor's office
7,430 04. Clinic
1,815 05. Health center
1,381 06. Hospital outpatient clinic
3,713 07. HMO/prepaid group
763 08. Military or VA health care
facility
268 09. Some other place
516 98. Not ascertained
114 99. DK or refused
10,256 Blank. NA - Does not have/DK
if have a usual source
of care
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
416 5b IS THERE PARTICULAR PERSON
USUALLY SEEN
44,452 1. Yes
6,290 2. No
587 8. Not ascertained
346 9. DK or refused
11,727 Blank. NA - Does not have/DK if
have a usual source
of care
______________________________________________________________________
417 6a TYPE OF HEALTH PROFESSIONAL
(Usually sees a particular person
when goes to usual source of care.
Q 5b = 1)
43,371 1. Doctor
79 2. Nurse
222 3. Nurse practitioner
180 4. Physician's assistant
43 5. Chiropractor
43 6. Some other professional
500 8. Not ascertained
14 9. DK or refused
18,950 Blank. NA
______________________________________________________________________
418 6b TYPE OF DOCTOR
(Usually sees a particular doctor
when goes to usual source of care
Q 6a = 1)
40,294 1. Family doctor/GP/
internist/pediatrician
1,047 2. Obstetrician/gynecologist
1,434 3. Other specialist
451 8. Not ascertained
145 9. DK or refused
20,031 Blank. NA
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
419 7 LAST TIME WENT TO USUAL
PLACE (Has a usual place
for medical care)
1,322 0. Hasn't been there
yet/never
20,540 1. Less than 3 months ago
9,747 2. At least 3 months,
less than 6 months ago
9,693 3. At least 6 months,
less than 1 year ago
6,342 4. At least 1 year,
less than 2 years ago
4,098 5. Two or more years ago
518 8. Not ascertained
886 9. DK or refused
10,256 Blank. NA
______________________________________________________________________
420 8 SAME PLACE FOR ROUTINE CARE
(Has a usual place for medical
care)
50,176 1. Yes
1,793 2. No
914 8. Not ascertained
263 9. DK or refused
10,256 Blank. NA
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
421 Recode RELATIONSHIP BETWEEN SOURCES OF
SICK AND PREVENTIVE CARE
50,176 1. Has the same usual source for
sick and routine/preventive care
1,793 2. Has a usual source for sick care,
but it is not usual source of
routine/routine/preventive care
(may include persons with no
usual source of
routine/preventive care)
1,177 3. Has a usual source of sick care,
but unknown if has a usual source
of routine/preventive care
81 4. Has two or more usual sources of
sick care and has a source for
routine/preventive care
84 5. Has two or more usual sources
of sick care, but does not
have a source for routine/
preventive care
27 6. Has two or more usual sources
of sick care, but unknown if
has a usual source of
routine/preventive care
7,123 7. No usual source of sick care;
not asked about preventive
care
2,722 8. Not ascertained
219 9. DK or refused
_____________________________________________________________________
422 9 GO TO OTHER PLACE PAST 12 MONTHS
(Has a usual place for medical
care)
15,094 1. Yes
36,270 2. No
1,397 8. Not ascertained
385 9. DK or refused
10,256 Blank. NA
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
423 10b CHANGED PLACE FOR ROUTINE CARE
4,548 1. Yes
55,862 2. No
2,841 8. Not ascertained
151 9. DK or refused
______________________________________________________________________
424-425 10d MAIN REASON FOR CHANGE LAST TIME
1,503 01. Changed residence
197 02. Changed jobs
643 03. Employer changed
insurance coverage
347 04. Former usual source
not available
4 05. Owed money to former source
673 06. Dissatisfied with former
source/like new source
better
308 07. Medical care needs changed
126 08. Former source stopped
taking insurance/coverage
639 09. Some other reason
103 98. Not ascertained
5 99. DK or refused
58,854 Blank. NA - Did not/DK change
usual place of medical
care in past 12 months
______________________________________________________________________
426 11b NEEDED CARE BUT NOT ABLE TO GET IT
1,703 1. Yes
58,773 2. No
2,792 8. Not ascertained
134 9. DK or refused
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
427-428 11d MAIN REASON DIDN'T GET CARE
801 01. Could not afford it
278 02. No insurance
32 03. Doctor did not
accept Medicaid/
insurance plan
50 04. Insurance didn't cover
30 05. Not serious enough
34 06. Wait too long in
clinic/office
141 07. Difficulty getting
an appointment
19 08. Doesn't like/trust/
believe in doctors
33 09. No doctor available
8 10. Didn't know where to go
14 11. No way to get there
7 12. Hours not convenient
0 13. Speak a different language
1 14. Health of another family
member interfered
9 15. Clinic/office not accessible
135 16. Other reason
106 98. Not ascertained
5 99. DK or refused
61,699 Blank. NA - Obtained medical
care when needed during
the past 12 months
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
429 11e LACK OF INSURANCE OR MONEY A REASON
121 1. Yes
316 2. No
102 3. Not ascertained
3 9. DK or refused
62,860 Blank. NA - Obtained medical care
when needed during the 12 months
or already mentioned that money
or lack of insurance was a reason
______________________________________________________________________
430 12b DELAYED SEEKING MEDICAL
CARE BECAUSE OF COST
4,507 1. Yes
55,972 2. No
2,812 8. Not ascertained
111 9. DK or refused
______________________________________________________________________
431 13b NEEDED DENTAL CARE BUT
COULD NOT GET IT
4,800 1. Yes
55,603 2. No
2,833 8. Not ascertained
166 9. DK or refused
______________________________________________________________________
432 14b NEEDED PRESCRIPTION MEDICINES
BUT COULD NOT GET THEM
1,504 1. Yes
58,945 2. No
2,781 8. Not ascertained
172 9. DK or refused
______________________________________________________________________
433 15b NEEDED EYEGLASSES BUT
COULD NOT GET THEM
1,874 1. Yes
58,379 2. No
2,947 8. Not ascertained
202 9. DK or refused
______________________________________________________________________
1996 NHIS ACCESS TO CARE PUBLIC USE FILE
______________________________________________________________________
File
Locations Item No. Frequency Items and Codes
______________________________________________________________________
434 16b NEEDED MENTAL HEALTH CARE
BUT COULD NOT GET IT
348 1. Yes
60,046 2. No
2,849 8. Not ascertained
159 9. DK or refused
______________________________________________________________________
435-436 - - BLANK
______________________________________________________________________
437-438 Check CHECK ITEM (Reference Person
Item A5 Only) PERSON WHO ANSWERED MOST
QUESTIONS
865 00. Respondent not ascertained
59,837 01-28. Person number
0 30-97. Person number
101 98. Active duty military
13 99. Non household member
2,586 Blank. Dummy record
______________________________________________________________________
439 Recode RESPONDENT FOR SUPPLEMENT STATUS
23,701 1. Self
36,319 2. Proxy
796 9. Unknown respondent
2,586 Blank. Dummy record
____________________________________________________________________
440 - - BLANK
______________________________________________________________________
APPENDIX A
There is no Appendix for this document
B-1
APPENDIX B
INDUSTRY RECODES OUTLINE Revised in 1995
_______________________________________________________________________________
Recodes
---------------------
No. 1 No. 2
Chrs. Chrs. Industry Title SIC Code*
80-81 82-83
_______________________________________________________________________________
01 01 AGRICULTURE 01-02,071-072,074-
076,078
02 01 FORESTRY AND FISHERIES 08-09
_______________________________________________________________________________
10 02 MINING 10,12-14
_______________________________________________________________________________
20 03 CONSTRUCTION 15-17
_______________________________________________________________________________
(30-34,
40-46) (04) MANUFACTURING:
(30-34) NONDURABLE GOODS
30 04 Food and kindred products 201-209
31 04 Textile mill and finished 221-229,231-239
textile products
32 04 Printing, publishing and 271-279
allied industries
33 04 Chemicals and allied 281-287,289
products
34 04 Other nondurable goods 21,261-263,265,267,
291,295,299,301-
306,308,311,313-
317,319
_______________________________________________________________________________
*Standard Industrial Classification
APPENDIX B
INDUSTRY RECODES OUTLINE Revised in 1995
_______________________________________________________________________________
Recodes
-----------------
No. 1 No. 2
Chrs. Chrs. Industry Title SIC Code*
80-81 82-83
_______________________________________________________________________________
(30-34,
40-46) (04) MANUFACTURING: - continued
(40-46) DURABLE GOODS
40 04 Furniture, lumber and wood 241-245,249,25
41 04 Primary metal industries 331-332,334,3331,
3334,3339,3351,
3353-3357,3363-
3366,3369,339
42 04 Fabricated metal 341-349
industries, including
ordnance
43 04 Machinery, except 351-359
electrical
44 04 Electrical machinery, 361-367,369
equipment and supplies
45 04 Transportation equipment 371-376,379
46 04 Other and not specified 321-329,381-382,
durable goods 384-387,39
_______________________________________________________________________________
*Standard Industrial Classification
APPENDIX B
INDUSTRY RECODES OUTLINE Revised in 1995
_______________________________________________________________________________
Recodes
-----------------
No. 1 No. 2
Chrs. Chrs. Industry Title SIC Code*
80-81 82-83
_______________________________________________________________________________
(50-54) (05) TRANSPORTATION, COMMUNICATIONS
AND OTHER PUBLIC UTILITIES
50 05 Railroads 40
51 05 Trucking service and 421-423
warehousing
52 05 Other transportation 41,43-47
53 05 Communications 481-484,489
54 05 Utilities and sanitary 491-497
_______________________________________________________________________________
60 06 WHOLESALE TRADE 501-509,511-519
_______________________________________________________________________________
*Standard Industrial Classification
APPENDIX B
INDUSTRY RECODES OUTLINE Revised in 1995
_______________________________________________________________________________
Recodes
-----------------
No. 1 No. 2
Chrs. Chrs. Industry Title SIC Code*
80-81 82-83
_______________________________________________________________________________
(61-65) (07) RETAIL TRADE
61 07 General merchandise stores 531,533,539
62 07 Food, bakery and dairy 541-546,549
stores
63 07 Automotive dealers and 551-557,559
gasoline stations
64 07 Eating and drinking places 58
65 07 Other and not specified 521,523,525-527,56,
retail trade 571-572,5731,5734-
5736,591-594,5961-
5963,598,5992-5995,
5999
_______________________________________________________________________________
(70-71) (08) FINANCE, INSURANCE, AND REAL
ESTATE
70 08 Banking and credit 60-61
agencies
71 08 Insurance, real estate, 62-65,67
and other finance
_______________________________________________________________________________
*Standard Industrial Classification
APPENDIX B
INDUSTRY RECODES OUTLINE Revised in 1995
_______________________________________________________________________________
Recodes
-----------------
No. 1 No. 2
Chrs. Chrs. Industry Title SIC Code*
80-81 82-83
_______________________________________________________________________________
(75-85) (09-12) SERVICES:
(75-76) (09) BUSINESS AND REPAIR SERVICES
75 09 Business services 731-738,751,752,
7542
76 09 Repair services 753,7549,762-764,
7692,7694,7699
(77-78) (10) PERSONAL SERVICES
77 10 Private households 88
78 10 Other personal services 701-704,721-726,729
79 11 ENTERTAINMENT AND 781-784,791-794,799
RECREATION SERVICES
(80-85) (12) PROFESSIONAL AND RELATED
SERVICES
80 12 Hospitals 806
81 12 Health services, except 801-803,8041-8043,
hospitals 8049,805,807-809
82 12 Elementary and secondary 821-822
schools and colleges
83 12 Other educational services 823-824,829
84 12 Social services, religious 832-833,835-836,
and membership 839,84,861-866,869
organizations
85 12 Legal, engineering and 81,871-874,899
other professional services
_______________________________________________________________________________
*Standard Industrial Classification
APPENDIX B
INDUSTRY RECODES OUTLINE Revised in 1995
_______________________________________________________________________________
Recodes
----------------
No. 1 No. 2
Chrs. Chrs. Industry Title SIC Code*
80-81 82-83
_______________________________________________________________________________
90 13 PUBLIC ADMINISTRATION 911-913,919,92-97
_______________________________________________________________________________
95 14 UNKNOWN INDUSTRY -
(Includes never worked)
_______________________________________________________________________________
96 14 REFUSED, CLASSIFIED, ETC.
_______________________________________________________________________________
97 15 NOT IN LABOR FORCE - codes Blank
and 8 in current activity recode
(loc. 75) (Under 18 or 18+ and
not in Labor Force).
_______________________________________________________________________________
98 16 ARMED FORCES (excludes Reserves
and National Guard)
_______________________________________________________________________________
*Standard Industrial Classification
APPENDIX B
INDUSTRY RECODE TITLES
_______________________________________________________________________________
Recode No. 1
Code Titles Inclusions
_______________________________________________________________________________
01 AGRICULTURE, FORESTRY AND FISHERIES 01,02
02 MINING 10
03 CONSTRUCTION 20
04 MANUFACTURING 30-34, 40-46
05 TRANSPORTATION, COMMUNICATIONS AND OTHER PUBLIC 50-54
UTILITIES
06 WHOLESALE TRADE 60
07 RETAIL TRADE 61-65
08 FINANCE, INSURANCE, AND REAL ESTATE 70-71
09 BUSINESS AND REPAIR SERVICES 75-76
10 PERSONAL SERVICES 77-78
11 ENTERTAINMENT AND RECREATION SERVICES 79
12 PROFESSIONAL AND RELATED SERVICES 80-85
13 PUBLIC ADMINISTRATION 90
14 UNKNOWN (includes never worked, refused, 95-96
classified, etc.)
15 NOT IN LABOR FORCE 97
16 ARMED FORCES 98
C-1
APPENDIX C
OCCUPATION RECODE OUTLINE Revised in 1995
__________________________________________________________________________
Recodes
----------------
No. 1 No. 2
Chrs. Chrs. Occupation Title SOC Code*
87-88 89-90
__________________________________________________________________________
(01-03) (01) EXECUTIVE, ADMINISTRATIVE, -
AND MANAGERIAL OCCUPATIONS
01 01 Officials and administrators, 111-113
public administration
02 01 Managers and administrators, 121-128,131-
except public administration 1344,1351-
1354,1359,
136-139
03 01 Management related occupations 1412,1414-1415,
1419,142-143,
1442-1443,1449,
145,1472-
1473,149
__________________________________________________________________________
*Standard Occupational Classification
APPENDIX C
OCCUPATION RECODE OUTLINE Revised in 1995
__________________________________________________________________________
Recodes
----------------
No. 1 No. 2
Chrs. Chrs. Occupation Title SOC Code*
87-88 89-90
__________________________________________________________________________
(04-11) (02) PROFESSIONAL SPECIALTY OCCUPATIONS -
04 02 Engineers 1622-1628,1632-
1637,1639
05 02 Architects and surveyors 161,164
06 02 Natural mathematical and 171-172,1732-
computer scientists 1733,1739,
1842-1843,
1845-1847,1849,
1852-1855
07 02 Health diagnosing occupations 261-262,27,281,
283,289
08 02 Health assessment and 29,301-302,
treating occupations 3031-3034,3039,
304
09 02 Teachers, librarians and 2212-2218,
Counselors 2222-2228,
2231-2238,
2242-2247,
2249,231-233,
235,236,239,24,
251,252
10 02 Writers, artists, 34,321-329,
entertainers and athletes 331-333,398
11 02 Other professional specialty 1912-1916,
occupations 1919,192,
2032-2033,
2042,2049,
211-212
__________________________________________________________________________
*Standard Occupational Classification.
APPENDIX C
OCCUPATION RECODE OUTLINE Revised in 1995
__________________________________________________________________________
Recodes
----------------
No. 1 No. 2
Chrs. Chrs. Occupation Title SOC Code*
87-88 89-90
___________________________________________________________________________
(12-13) (03) TECHNICIANS AND RELATED -
SUPPORT OCCUPATIONS
12 03 Health technologists and 362-366,369
technicians
13 03 Technologists, technicians 3711-3713,3719,
except health 372-373,382,
3831-3833,
384,389,
392-393,396,
3971-3972,
3974,399,
825
___________________________________________________________________________
(14-16) (04) SALES OCCUPATIONS -
14 04 Supervisors and proprietors 40
15 04 Sales representatives, 4122-4124,
commodities and finance 4152-4153,
421,423-424
16 04 Other sales 4342-4348,4351-
4354,4356,4359,
4362-4367,4369,
444-447,449
__________________________________________________________________________
*Standard Occupational Classification
APPENDIX C
OCCUPATION RECODE OUTLINE Revised in 1995
__________________________________________________________________________
Recodes
----------------
No. 1 No. 2
Chrs. Chrs. Occupation Title SOC Code*
87-88 89-90
___________________________________________________________________________
(17-21) (05) ADMINISTRATIVE SUPPORT -
OCCUPATIONS, INCLUDING CLERICAL
17 05 Computer equipment operators 4612-4613
18 05 Secretaries, stenographers 4622-4624
and typists
19 05 Financial records processing 4712-4713,
occupations 4715-4716,
4718
20 05 Mail and message distributing 4742-4745
21 05 Other administrative support 4511-4514,4516,
4519,4521-4529,
463,4642-4645,
4649,4662-4664,
4692,4694,4696,
4699,4722-4723,
4729,4732-4733,
4739,4751-4759,
4782-4784,4786-
4787,4791-4795,
4799
22 06 Private household occupations 502-507,509
___________________________________________________________________________
*Standard Occupational Classification.
APPENDIX C
OCCUPATION RECODE OUTLINE Revised in 1995
___________________________________________________________________________
Recodes
----------------
No. 1 No. 2
Chrs. Chrs. Occupation Title SOC Code*
87-88 89-90
___________________________________________________________________________
(23-24) (07) PROTECTIVE SERVICE OCCUPATIONS
23 07 Police and firefighters 5111-5112,
5122-5123,
5132-5134
24 07 Other protective service 5113,5142,5144,
occupations 5149
___________________________________________________________________________
(25-28) (08) SERVICE OCCUPATIONS, EXCEPT
PROTECTIVE AND HOUSEHOLD
25 08 Food service 5211-5219
26 08 Health service 5232-5233,5236
27 08 Cleaning and building service 5241-5242,
5244-5246,5249
28 08 Personal service 5251-5258,5262-
5264,5269
___________________________________________________________________________
(29-31) (09) FARMING, FORESTRY AND FISHING
OCCUPATIONS
29 09 Farm operators and managers 5512-5515,5522-
5525
30 09 Farm workers and other 5611-5619,
agricultural workers 5621-5622,
5624-5625,5627
31 09 Forestry and fishing 571-573,579,
occupations 583-584,8241(pt.)
___________________________________________________________________________
*Standard Occupational Classification.
APPENDIX C
OCCUPATION RECODE OUTLINE Revised in 1995
___________________________________________________________________________
Recodes
----------------
No. 1 No. 2
Chrs. Chrs. Occupation Title SOC Code*
87-88 89-90
___________________________________________________________________________
(32-34) (10) PRECISION PRODUCTION, CRAFT
AND REPAIR OCCUPATIONS
32 10 Mechanics and repairers 60,6111-6118,
613-614,6151-
6159,616,6171-
6179
33 10 Construction and extractive 6311-6316,6318,
trades 632,6412-
6414(pt.),6422,
6424,6432-6433,
6442-6444,645,
6462-6468,6472-
6476,6479,652-
654,656
34 10 Precision production 67,71,
occupations 6811-6814,
6816-6817,
6821-6824,
6829,6831-6832,
6835,6839,6844,
6852-6854,6856,
6859,6861-6862,
6864-6867,6869,
6871-6873,6879,
6881-6882,691-
696,7477(pt.),
7668,7677(pt.),
7752,828
___________________________________________________________________________
*Standard Occupational Classification
APPENDIX C
OCCUPATION RECODE OUTLINE Revised in 1995
___________________________________________________________________________
Recodes
----------------
No. 1 No. 2
Chrs. Chrs. Occupation Title SOC Code*
87-88 89-90
___________________________________________________________________________
OPERATORS, FABRICATORS AND
LABORERS
(35-36) (11) MACHINE OPERATORS, ASSEMBLERS
AND INSPECTORS
35 11 Machine operators and 6841-6842,6849,
tenderers, except precision 6855,6863,6868,
7312-7319,7322,
7324,7326,7329,
7339,7342-7344,
7349,7431-7435,
7439,7443-7444,
7449,7451-7452,
7459,7462-7463,
7467,7472,7474,
7476-7478,7479,
7512-7519,7522,
7529,7539,7542-
7544,7549,7631-
7636,7639,7642-
7644,7649,7651-
7652,7654-7659,
7661-7667,7669,
7671-7676,
7677(pt.),
7678-7679
36 11 Fabricators, assemblers, 7332-7333,7532-
inspectors and samplers 7533,7714,7717,
72,774,7753-
7759,782-785,787
___________________________________________________________________________
*Standard Occupational Classification
APPENDIX C
OCCUPATION RECODE OUTLINE Revised in 1995
___________________________________________________________________________
Recodes
----------------
No. 1 No. 2
Chrs. Chrs. Occupation Title SOC Code*
87-88 89-90
___________________________________________________________________________
(37-39) (12) TRANSPORTATION AND MATERIAL
MOVING OCCUPATIONS
37 12 Motor vehicle operators 8111,8212-8216,
8218-8219,874
38 12 Other transportation, except 8113,8232-8233,
motor vehicles 8239,8241(pt.),
8242-8245
39 12 Material moving equipment 812,8312-8319
operators
___________________________________________________________________________
(40-41) (13) HANDLERS, EQUIPMENT CLEANERS,
HELPERS AND LABORERS
40 13 Construction laborers 871
41 13 Freight, stock and material 85,861-863,
handlers 8641-8646,
8648,865,
8722-8726,873,
875,8761,8769
___________________________________________________________________________
* Standard Occupational Classification
APPENDIX C
OCCUPATION RECODE OUTLINE Revised in 1995
___________________________________________________________________________
Recodes
----------------
No. 1 No. 2
Chrs. Chrs. Occupation Title SOC Code*
87-88 89-90
___________________________________________________________________________
95 14 UNKNOWN OCCUPATION
(Includes never worked)
___________________________________________________________________________
96 14 REFUSED, CLASSIFIED, ETC.
___________________________________________________________________________
97 15 NOT IN LABOR FORCE - codes Blank
and 8 in current activity recode
(Loc. 75). (Under 18 or 18+
and Not in Labor Force)
___________________________________________________________________________
98 16 MILITARY
___________________________________________________________________________
*Standard Occupational Classification
APPENDIX C
OCCUPATION RECODE TITLES
___________________________________________________________________________
Recode No. 1
Code Titles Inclusions
___________________________________________________________________________
MANAGERIAL AND PROFESSIONAL SPECIALTY OCCUPATIONS
01 EXECUTIVE, ADMINISTRATIVE AND MANAGERIAL OCCUPATIONS 01-03
02 PROFESSIONAL SPECIALTY OCCUPATIONS 04-11
TECHNICAL, SALES AND ADMINISTRATIVE SUPPORT
OCCUPATIONS
03 TECHNICIANS AND RELATED SUPPORT OCCUPATIONS 12-13
04 SALES OCCUPATIONS 14-16
05 ADMINISTRATIVE SUPPORT OCCUPATIONS, INCLUDING 17-21
CLERICAL
SERVICE OCCUPATIONS
06 PRIVATE HOUSEHOLD OCCUPATIONS 22
07 PROTECTIVE SERVICE OCCUPATIONS 23-24
08 SERVICE OCCUPATIONS, EXCEPT PROTECTIVE AND 25-28
HOUSEHOLD
09 FARMING, FORESTRY AND FISHING OCCUPATIONS 29-31
10 PRECISION PRODUCTION, CRAFT AND REPAIR OCCUPATIONS 32-34
OPERATORS, FABRICATORS AND LABORERS
11 MACHINE OPERATORS, ASSEMBLERS AND INSPECTORS 35-36
12 TRANSPORTATION AND MATERIAL MOVING OCCUPATIONS 37-39
13 HANDLERS, EQUIPMENT CLEANERS, HELPERS AND LABORERS 40-41
14 UNKNOWN OCCUPATION (includes never worked, refused, 95-96
classified, etc.)
15 NOT IN LABOR FORCE 97
16 MILITARY 98
VARIANCE ESTIMATION FOR PERSON DATA USING THE
NHIS PUBLIC USE PERSON DATA TAPE, 1995-2004
April 17, 1998
About this document:
This document provides basic design information about the 1995-2004 NHIS and
presents methods to compute standard errors for each annually released person-
level database. This document focuses upon a full-sample NHIS Core survey that
is anticipated for each data collection year. For some years the full-sample
methods need to be modified to account for design changes. In particular, the
1996 NHIS has a sample design quite different from the 1995 NHIS. Also,
Supplemental surveys may require modified methods. Some notes about these
modifications appear at the end of this document.
Contents
VARIANCE ESTIMATION FOR PERSON DATA USING THE NHIS PUBLIC
USE PERSON DATA TAPE, 1995 Pages 2-11
Notes for the 1995 NHIS Year 2000 supplement Page 12
Notes for the 1996 NHIS Pages 13-16
VARIANCE ESTIMATION FOR PERSON DATA USING THE
NHIS PUBLIC USE PERSON DATA TAPE, 1995
Introduction: The data collected in the NHIS are obtained through a complex
sample design involving stratification, clustering, and multistage sampling,
and the final weights are subject to several adjustments. Any variance
estimation methodology must involve numerous simplifying assumptions about
the design and weighting. We provide some oversimplified conceptual NHIS
design structures that should allow users of this Public Use Data Set to
compute reasonably accurate standard errors.
There are several available software packages for analyzing complex samples.
A comparison is beyond the scope of this document, but an Internet web page
Summary of Survey Analysis Software currently located at
http://www.fas.harvard.edu/~stats/survey-soft/survey-soft.html provides
references and discussion. At NCHS the software package SUDAAN has been used
to produce standard errors. In this document SAS and SUDAAN computer code
is provided, but without guarantees of any kind. The computer code and
methods are subject to change without notification to the user. The entire
risk as to the results and performance is assumed by the user. NCHS
recommends that any analysis of NHIS data be done under the supervision of a
statistician who understands the implications of complex-sample design
surveys.
Conceptual NHIS design for 1995 The U.S. Bureau of the Census partitions the
state counties or equivalents along with metropolitan areas into a universe
of about 1900 Primary Sampling Units (PSUs) (note, PSUs may be combined
counties) to provide the primary sampling areas for its many national
surveys. For the NHIS these universe PSUs are partitioned into geographical
strata at the state level. Some of the larger universe PSUs are self-
representing (SR), i.e., they are in the NHIS with certainty. The other PSUs
are called non-self-representing (NSR) or non-certainty PSUs. Within each
state the NSR PSUs are partitioned into strata based upon similarity of PSU
characteristics. Within each NSR stratum 2 PSUs are selected using Durbin's
probability proportional to size (PPS) sampling method using the population
as a measure of size. (In some smaller states only 1 PSU is drawn PPS). The
SR PSUs are equivalent to strata, but historically they have been referred to
as PSUs. (PPS and Durbin sampling are discussed in Chapter 9A of Cochran
(1977)).
Within a sampled NSR or SR PSU the geography is partitioned into smaller
geographical clusters which are used to form the universe of secondary
sampling units (SSUs). These SSUs are then partitioned into density strata
based upon black and Hispanic population concentration as determined by the
1990 Decennial Census. An additional strata for new construction since the
last Decennial Census is also created. Within each density stratum SSUs are
sampled at different rates to meet different design objectives. Within each
sample SSU, all households containing black or Hispanic persons are sampled,
while all other households are subsampled. Supplemental NHIS surveys may
require additional sampling at SSU, household, or family levels.
The fundamental sampling weights are created such that under ideal sampling
conditions, unbiased estimators for each level of sampling are available.
In practice, however, the final sampling weights are adjusted for non-
response, and ratio adjusted. Furthermore, in 1995 a government shutdown
resulted in three lost weeks of sample which resulted in further weighting
adjustments. The most important adjustment is a quarterly post-
stratification to 90 age/sex/race/ethnicity Census control totals.
For variance estimation purposes, NCHS treats the NHIS as a two-stage sample.
The PSU probabilities of selection are known, and the SSUs are treated as
sampled with replacement within PSU density strata. Sampling weights are
adjusted by postratification. With these assumptions the SUDAAN software is
used to compute variances. Much of the design information, state, density
strata, and Durbin probabilities can be used to identify the smaller
geographical areas. NCHS forbids the disclosure of information which may
compromise the confidentiality promised to survey respondents, so some design
information is not provided with the Public Use Data. While all design
information is not available to the public, variance estimation methods
exist which provide similar results to the NCHS internally used
methodology. Two methods are described below.
Design Information Available on the NHIS Public Use Databases.
CAUTION For 1996 databases, refer to the Notes at the end of this document.
The following variables are used to produce code for variance estimation.
Field locations below are from the PERSON level database, but may change on
other databases; the user should check the file documentation.
Variable Tape
Name Location Field Label
STRAT_V 337-340 'STRATA FOR VARIANCE ESTIMATION'
PSU_V 341 'PSU FOR VARIANCE ESTIMATION'
SUB_V 342-343 'SUBSTRATUM FOR VARIANCE ESTIMATION'
SSU 344-350 'SECONDARY SAMPLING UNIT'
PANEL 352 'PANEL 4'
TYPE_PSU 351 'TYPE OF PSU'
WTF 219-227 'FINAL BASIC WEIGHT'
Two methods of variance estimation are provided.
Method 1 - 187 Strata containing 2 PSUs per stratum sampled with replacement
Here, the NHIS universe has been partitioned into 187 strata. Most of the
original NHIS strata and PSUs retain their original sampling structure with
two PSUs being sampled per stratum, but a few strata have been collapsed, and
in the largest self-representing strata, two pseudo-PSUs have been created.
All PSUs are treated as sampled with replacement within their respective
strata. This method will provide somewhat conservative standard errors,
and the standard error estimator itself has less stability than the standard
error estimator described by Method 2 below. Method 1 should be applicable
to many complex survey sample design computer programs which require exactly
2 sampled PSUs per stratum. This method is robust when analyzing subsetted
data (See the section "Subsetted Data Analysis" below).
Coding required (SAS code provided):
STRATUM = STRAT_V;
PSU = PANEL;
IF (PSU_V = 5) THEN PSU = INT((PANEL + 1)/2);
IF(PSU_V = 8) THEN STRATUM = 553;
IF((TYPE_PSU = 1) AND (PSU_V IN (2,4))) THEN STRATUM =
(STRAT_V -1);
IF((STRAT_V = 921) AND (PSU_V = 3)) THEN STRATUM = 901;
As a check the user should observe 374 PSUs when using the full database.
For the above simplification of the NHIS sample design structure, the
following SUDAAN design statements may be used. (Note, the input file must
first be sorted by STRATUM and PSU variables.)
PROC ... DESIGN = WR;
NEST STRATUM PSU ;
WEIGHT WTF;
See the Section "Worked SUDAAN Examples" below for further discussion.
Method 2 - Multiple PSUs per Stratum design sampled with replacement
This method provides for more statistically efficient variance estimation
than Method 1, since it makes better use of the sampling design information.
Its application is limited to software that can handle multiple PSUs per
stratum, e.g., SUDAAN. For this method the original certainty PSUs are
partitioned by aggregations of the original race-ethnic density strata used
in sampling. The first randomly sampled unit is actually the SSU variable
which is now treated as the PSU variable. (Note, a certainty PSU unit
contributes nothing to the variance at the PSU sampling level.) Non-
certainty-strata PSUs are treated as being sampled with replacement within
their respective strata. Except for a few special cases, the non-certainty
PSUs have exactly the same structure in both Methods 1 and 2.
Coding required, (SAS code provided ):
IF TYPE_PSU = 1 THEN DO; /* certainty strata PSUs */
STRATUM = STRAT_V*1000 + SUB_V;
PSU = SSU ;
END;
ELSE DO ; /* non-certainty PSU */;
STRATUM = STRAT_V ;
PSU = PSU_V ;
END;
As a check, the user should observe the following counts:
Certainty Strata PSUs 4079
Non-certainty Strata PSUs 259
Total PSUs 4338
For the Method 2 design structure, the following SUDAAN design statements
may be used. (Note, the input file must first be sorted by STRATUM and PSU
variables.)
PROC ... DESIGN = WR;
NEST STRATUM PSU;
WEIGHT WTF;
See the Section "Worked SUDAAN Examples" for further discussion.
CAUTION. Method 2 should only be used on a full sample person data base.
Using this method with subsetted data may lead to incorrectly computed
standard errors. (See the section "Subsetted Data Analysis" below). If
using a subsetted data set, the user should check the degree of agreement
of the certainty and non-certainty counts with the values presented above.
CAUTION
A typically used rule-of-thumb for degrees of freedom to associate with a
standard error is the quantity (number of PSUs - number of strata). This
rule assumes that the PSUs are somewhat comparable in size. For Method 2
this rule may be grossly inaccurate since the concept of PSU is quite
different for certainty and non-certainty strata. Certainty strata PSUs of
Method 2 have small weighted values relative to those of non-certainty PSUs.
The rule-of-thumb degrees of freedom for Method 1 is 187, and Method 2 should
have a "true" degrees of freedom exceeding that of Method 1. However, for
practical purposes, any degrees of freedom exceeding 120 can be treated as
infinite, i.e., one uses a normal Z-statistic instead of a t-statistic for
testing. Note, that a one-tailed critical t0.025 at 120 degrees of freedom
is 1.98 while at an infinite degrees of freedom (i.e., a z-value) is 1.96.
If a variable of interest covers most of the NHIS PSUs, the limiting value
would probably be adequate for analysis. The user should consult a
mathematical statistician for discussion of degrees of freedom.
SUBSETTED DATA ANALYSES
Frequently, studies of NHIS variables are restricted to select subdomains,
e.g., persons aged 65 and older. To save on storage the user may delete all
records outside of the domain of interest. This procedure of keeping only
select records is called subsetting the data. With a subsetted data set one
can produce correct point estimates, e.g., the subdomain means, but standard
errors may be computed incorrectly when using a compromised design structure.
For example, if a stratum of Method 2 contains 10 PSUs and 5 are lost because
of subsetting, a SUDAAN run on the subsetted data will use an incorrect
formula to compute stratum contributions to the variance. If the full data
are run, SUDAAN correctly handles the 5 empty PSUs. Note, that SUDAAN has a
SUBPOPN option that allows the targeting of a subdomain from a full design
data base. (See the SUDAAN manual for details).
Subsetting methods with SUDAAN
Strategy 1. Use Method 1 above with the MISSUNIT option on the NEST
statement -
NEST STRATUM PSU/MISSUNIT ;
If a WR design has exactly 2 PSUs per stratum and some PSUs are removed from
the database then the SUDAAN MISSUNIT option performs a fix-up which produces
a standard error identical to that achieved when using a full data set and
SUBPOPN statement. Note, other output like design effects, degrees of
freedom, standardization may be computed differently. The user is
responsible for checking that subsetted input leads to correct results.
Strategy 2. Use Method 1 or 2 above on a "fixed-up" subsetted data set.
Basically, one needs to add some dummy records containing full design
information to the subsetted data set. To do this follow these instructions:
1. Create a 2-variable file containing STRATUM and PSU for each record of the
full person file ( 100,000+ records )
2. Sort this file by STRATUM and PSU within STRATUM.
3. Keep only 1 record for each PSU
add WTF = 10 -10 as a very small weight
add variable DUMMY = 0 to designate dummy record
A file, called DESIGN containing 4 variables with
374 records ( Method 1 used) or with
4338 records (Method 2 used) is created
4. Append DESIGN to the original subsetted database, called DATASET, to form
a new set, called DATANEW.
Define DUMMY = 1 on the DATASET component.
On the DESIGN component records define all variables other than STRATUM,
PSU, WTF, DUMMY as missing ".".
5. Sort DATANEW by STRATUM PSU
6. In SUDAAN use a "SUBPOPN DUMMY = 1;" line to direct SUDAAN to restrict
estimation to the subdomain of interest.
With the above fix-up SUDAAN will correctly handle empty PSUs when computing
the standard errors. SUDAAN output that needs the entire full sample
database for correct computation, e.g., design effects, may or may not be
appropriate. See the SUDAAN manual for computational forms or consult with
a mathematical statistician for correct interpretation.
Other notes on Subsetting data:
If a subsetted database under Method 2 has only a few missing PSUs, the
subsetted database can probably be run with SUDAAN without being fixed up.
For example, a subsetting by SEX will most likely result in all PSUs still
being in sample, but black males aged 65 and older would result in the loss
of many PSUs. The impact of running SUDAAN on uncorrected subsetted data
varies. Frequently, subsetted runs produce results consistent with those run
on a full data set, but sometimes they do not.
Subsetting by aggregates of Strata does not need a fix-up.
The condition, doctor visit, and hospital record databases are actually
subsetted files. To use with SUDAAN properly, the information should be
linked back to the appropriate person on the person file. Some statistics,
based upon aggregation of records, may be computed directly from this file
along with the fix-up. Consult with a statistician for appropriate SUDAAN
usage.
WORKED SUDAAN EXAMPLES
In the following runs the variables used are
LDR = proportion of persons without a doctor visit in the last 2 years
TDV_R = mean number of annual doctor visits (based upon 2 week recall)
HLT_FP = proportion of persons with self-reported fair or poor health status
(omitting missing)
AGE2: 1 = aged less than 18
2 = aged 18 to 44
3 = aged 45 to 64
4 = aged 65 and older
The following SUDAAN code was executed for both Method 1 and Method 2:
Caution The output presented below is based upon a preliminary NHIS Public
Use database. Your Public Use database may produce slightly different SUDAAN
output.
PROC DESCRIPT DATA = HIS.infile FILETYPE=SAS DESIGN = WR;
NEST STRATUM PSU ;
WEIGHT WTF;
VAR LDR TDV_R HLT_FP ;
SUBGROUP SEX AGE2;
LEVELS 2 4;
TABLES SEX AGE2;
PRINT NSUM WSUM MEAN SEMEAN
/ WSUMFMT=F10.0 MEANFMT=F8.5 SEMEANFMT=F8.5 ;
Method 1: partial output:
S U D A A N
Software for the Statistical Analysis of Correlated Data
Copyright Research Triangle Institute April 1996
Release 7.00
Number of observations read : 102467 Weighted count :261889548
Number of observations skipped : 0
(WEIGHT variable nonpositive)
Denominator degrees of freedom : 187
Research Triangle Institute
The DESCRIPT Procedure
by: Variable, SEX.
-----------------------------------------------------------------------------
| Variable | | SEX
| | | Total | 1 | 2 |
-----------------------------------------------------------------------------
| LDR | Sample Size | 102467 | 48809 | 53658 |
| | Weighted Size | 261889549 | 127570237 | 134319312 |
| | Mean | 0.13797 | 0.18013 | 0.09793 |
| | SE Mean | 0.00178 | 0.00250 | 0.00178 |
-----------------------------------------------------------------------------
| TDV_R | Sample Size | 102467 | 48809 | 53658 |
| | Weighted Size | 261889549 | 127570237 | 134319312 |
| | Mean | 5.90759 | 4.90385 | 6.86089 |
| | SE Mean | 0.09060 | 0.10039 | 0.12407 |
-----------------------------------------------------------------------------
| HLT_FP | Sample Size | 101277 | 48266 | 53011 |
| | Weighted Size | 258963568 | 126221708 | 132741859 |
| | Mean | 0.10126 | 0.09124 | 0.11079 |
| | SE Mean | 0.00157 | 0.00188 | 0.00176 |
-----------------------------------------------------------------------------
Method 1: partial output:
S U D A A N
Software for the Statistical Analysis of Correlated Data
Copyright Research Triangle Institute April 1996
Release 7.00
Number of observations read : 102467 Weighted count :261889548
Number of observations skipped : 0
(WEIGHT variable nonpositive)
Denominator degrees of freedom : 187
Research Triangle Institute
The DESCRIPT Procedure
by: Variable, AGE2.
-----------------------------------------------------------------------------
| Variable | | AGE2
| | | Total | 1 | 2 |
-----------------------------------------------------------------------------
| LDR | Sample Size | 102467 | 29711 | 40801 |
| | Weighted Size | 261889549 | 70670755 | 108040689 |
| | Mean | 0.13797 | 0.08894 | 0.18489 |
| | SE Mean | 0.00178 | 0.00269 | 0.00268 |
-----------------------------------------------------------------------------
| TDV_R | Sample Size | 102467 | 29711 | 40801 |
| | Weighted Size | 261889549 | 70670755 | 108040689 |
| | Mean | 5.90759 | 4.29682 | 4.88589 |
| | SE Mean | 0.09060 | 0.09797 | 0.12432 |
-----------------------------------------------------------------------------
| HLT_FP | Sample Size | 101277 | 29183 | 40423 |
| | Weighted Size | 258963568 | 69438212 | 107054300 |
| | Mean | 0.10126 | 0.02552 | 0.06610 |
| | SE Mean | 0.00157 | 0.00129 | 0.00168 |
-----------------------------------------------------------------------------
----------------------------------------------------------------
| Variable | | | |
| | | 3 | 4 |
----------------------------------------------------------------
| LDR | Sample Size | 20000 | 11955 |
| | Weighted Size | 51713265 | 31464840 |
| | Mean | 0.14461 | 0.07606 |
| | SE Mean | 0.00293 | 0.00251 |
----------------------------------------------------------------
| TDV_R | Sample Size | 20000 | 11955 |
| | Weighted Size | 51713265 | 31464840 |
| | Mean | 7.08504 | 11.09843 |
| | SE Mean | 0.17859 | 0.30642 |
----------------------------------------------------------------
| | | | |
| HLT_FP | Sample Size | 19834 | 11837 |
| | Weighted Size | 51315866 | 31155190 |
| | Mean | 0.16651 | 0.28344 |
| | SE Mean | 0.00356 | 0.00519 |
----------------------------------------------------------------
Method 2 Partial Output
S U D A A N
Software for the Statistical Analysis of Correlated Data
Copyright Research Triangle Institute April 1996
Release 7.00
Number of observations read : 102467 Weighted count :261889548
Number of observations skipped : 0
(WEIGHT variable nonpositive)
Denominator degrees of freedom : 4030
Research Triangle Institute
The DESCRIPT Procedure
by: Variable, SEX.
-----------------------------------------------------------------------------
| Variable | | SEX
| | | Total | 1 | 2 |
-----------------------------------------------------------------------------
| LDR | Sample Size | 102467 | 48809 | 53658 |
| | Weighted Size | 261889549 | 127570237 | 134319312 |
| | Mean | 0.13797 | 0.18013 | 0.09793 |
| | SE Mean | 0.00174 | 0.00231 | 0.00184 |
-----------------------------------------------------------------------------
| TDV_R | Sample Size | 102467 | 48809 | 53658 |
| | Weighted Size | 261889549 | 127570237 | 134319312 |
| | Mean | 5.90759 | 4.90385 | 6.86089 |
| | SE Mean | 0.07704 | 0.08503 | 0.11403 |
-----------------------------------------------------------------------------
| HLT_FP | Sample Size | 101277 | 48266 | 53011 |
| | Weighted Size | 258963568 | 126221708 | 132741859 |
| | Mean | 0.10126 | 0.09124 | 0.11079 |
| | SE Mean | 0.00152 | 0.00174 | 0.00182 |
-----------------------------------------------------------------------------
Method 2 Partial Output
S U D A A N
Software for the Statistical Analysis of Correlated Data
Copyright Research Triangle Institute April 1996
Release 7.00
Number of observations read : 102467 Weighted count :261889548
Number of observations skipped : 0
(WEIGHT variable nonpositive)
Denominator degrees of freedom : 4030
Research Triangle Institute
The DESCRIPT Procedure
by: Variable, AGE2.
-----------------------------------------------------------------------------
| Variable | | AGE2
| | | Total | 1 | 2 |
-----------------------------------------------------------------------------
| LDR | Sample Size | 102467 | 29711 | 40801 |
| | Weighted Size | 261889549 | 70670755 | 108040689 |
| | Mean | 0.13797 | 0.08894 | 0.18489 |
| | SE Mean | 0.00174 | 0.00271 | 0.00254 |
-----------------------------------------------------------------------------
| TDV_R | Sample Size | 102467 | 29711 | 40801 |
| | Weighted Size | 261889549 | 70670755 | 108040689 |
| | Mean | 5.90759 | 4.29682 | 4.88589 |
| | SE Mean | 0.07704 | 0.09116 | 0.11805 |
-----------------------------------------------------------------------------
| HLT_FP | Sample Size | 101277 | 29183 | 40423 |
| | Weighted Size | 258963568 | 69438212 | 107054300 |
| | Mean | 0.10126 | 0.02552 | 0.06610 |
| | SE Mean | 0.00152 | 0.00118 | 0.00157 |
-----------------------------------------------------------------------------
----------------------------------------------------------------
| Variable | |
| | | 3 | 4 |
----------------------------------------------------------------
| LDR | Sample Size | 20000 | 11955 |
| | Weighted Size | 51713265 | 31464840 |
| | Mean | 0.14461 | 0.07606 |
| | SE Mean | 0.00303 | 0.00269 |
----------------------------------------------------------------
| TDV_R | Sample Size | 20000 | 11955 |
| | Weighted Size | 51713265 | 31464840 |
| | Mean | 7.08504 | 11.09843 |
| | SE Mean | 0.16109 | 0.28387 |
----------------------------------------------------------------
| HLT_FP | Sample Size | 19834 | 11837 |
| | Weighted Size | 51315866 | 31155190 |
| | Mean | 0.16651 | 0.28344 |
| | SE Mean | 0.00351 | 0.00501 |
----------------------------------------------------------------
Best NHIS design using Durbin probabilities (not available to the public)
and weights adjusted by post-stratification
-----------------------------------------------------------------------------
| Variable | | SEX
| | | Total | 1 | 2 |
-----------------------------------------------------------------------------
| LDR | Sample Size | 102467 | 48809 | 53658 |
| | Weighted Size | 261889549 | 127570237 | 134319312 |
| | Mean | 0.13784 | 0.17991 | 0.09789 |
| | SE Mean | 0.00170 | 0.00221 | 0.00182 |
-----------------------------------------------------------------------------
| TDV_R | Sample Size | 102467 | 48809 | 53658 |
| | Weighted Size | 261889549 | 127570237 | 134319312 |
| | Mean | 5.90468 | 4.89733 | 6.86141 |
| | SE Mean | 0.07511 | 0.08320 | 0.11217 |
-----------------------------------------------------------------------------
| HLT_FP | Sample Size | 101277 | 48266 | 53011 |
| | Weighted Size | 258974266 | 126232939 | 132741328 |
| | Mean | 0.10127 | 0.09125 | 0.11080 |
| | SE Mean | 0.00137 | 0.00159 | 0.00165 |
-----------------------------------------------------------------------------
Best NHIS design using Durbin probabilities (not available to the public)
and weights adjusted by post-stratification
Post-stratified estimates
by: Variable, AGE2.
-----------------------------------------------------------------------------
| Variable | | AGE2
| | | Total | 1 | 2 |
-----------------------------------------------------------------------------
| LDR | Sample Size | 102467 | 29711 | 40801 |
| | Weighted Size | 261889549 | 70670755 | 108040689 |
| | Mean | 0.13784 | 0.08845 | 0.18484 |
| | SE Mean | 0.00170 | 0.00258 | 0.00248 |
-----------------------------------------------------------------------------
| TDV_R | Sample Size | 102467 | 29711 | 40801 |
| | Weighted Size | 261889549 | 70670755 | 108040689 |
| | Mean | 5.90468 | 4.29787 | 4.87876 |
| | SE Mean | 0.07511 | 0.09066 | 0.11858 |
-----------------------------------------------------------------------------
| HLT_FP | Sample Size | 101277 | 29183 | 40423 |
| | Weighted Size | 258974266 | 69441900 | 107059972 |
| | Mean | 0.10127 | 0.02555 | 0.06624 |
| | SE Mean | 0.00137 | 0.00116 | 0.00153 |
-----------------------------------------------------------------------------
----------------------------------------------------------------
| Variable | |
| | | 3 | 4 |
----------------------------------------------------------------
| LDR | Sample Size | 20000 | 11955 |
| | Weighted Size | 51713265 | 31464840 |
| | Mean | 0.14484 | 0.07587 |
| | SE Mean | 0.00298 | 0.00268 |
----------------------------------------------------------------
| TDV_R | Sample Size | 20000 | 11955 |
| | Weighted Size | 51713265 | 31464840 |
| | Mean | 7.08472 | 11.09687 |
| | SE Mean | 0.16180 | 0.27613 |
----------------------------------------------------------------
| HLT_FP | Sample Size | 19834 | 11837 |
| | Weighted Size | 51315313 | 31157082 |
| | Mean | 0.16633 | 0.28322 |
| | SE Mean | 0.00342 | 0.00487 |
----------------------------------------------------------------
Remark on Examples
A comparison of the three SUDAAN examples shows that Method 2 performs quite
well when compared to the "best" internal NCHS variance design for the NHIS.
Based on limited preliminary evidence, it appears that for means, Method 2
typically provides standard errors in close agreement with, while slightly
larger than, the standard errors produced by the NCHS "best" method. Method 1
tends to provide slightly larger standard errors than Method 2 does, although
the sample output does include examples where the Method 1 standard error is
smaller than the Method 2 standard error.
Reference:
(1977) Cochran, W. G., Sampling techniques (3rd ed), John Wiley & Sons
Notes for Year 2000 application (added 01/21/98)
The variance estimation methods of this document may be applied to the
Year 2000 Objectives Public Use File. The following changes must be made:
The design information variables are all in the same file locations with the
exception of "WTF".
Substitute:
WTF 207-212 'FINAL BASIC WEIGHT'
The PSU check for method 2 should now read:
As a check, the user should observe the following counts:
Certainty Strata PSUs 3804
Non-certainty Strata PSUs 259
Total PSUs 4063
Notes on the 1996 NHIS (added 04/17/98)
In 1996 the NHIS survey underwent a transition from a paper-and-pencil to a
computer-assisted interview process. This transition resulted in roughly
5/8 of the available full sample being targeted for processing and public
release. In 1997 the full sample was again implemented. For 1996 the reader
should substitute the information on pages 3 and 4 and the top of page 5:
Design Information Available on the NHIS Public Use Databases.
Method 1 - 187 Strata containing 2 PSUs per stratum sampled with replacement
Method 2 - Multiple PSUs per Stratum design sampled with replacement
with the 1996 information on the following pages:
Design Information Available on the 1996 NHIS Public Use Databases.
The following variables are used to produce code for variance estimation.
Field locations below are from the PERSON level database, but may change on
other databases; the user should check the file documentation.
Variable
Name Location Field Label
STRAT96* 354-357 'COLLAPSED VARIANCE STRATUM'
PSU96* 358 'VARIANCE PSU'
SUB_V 342-343 'SUBSTRATUM FOR VARIANCE ESTIMATION'
SSU 344-350 'SECONDARY SAMPLING UNIT'
PANEL 352 'PANEL 4'
NSR96* 353 'NSR STATUS VARIABLE'
WTF 219-227 'FINAL BASIC WEIGHT'
(*indicates modified design variables added to the 1996 databases)
Two methods of variance estimation are now provided.
Method 1.96 -98 Strata containing 3 PSUs per stratum sampled with replacement
Here, the NHIS universe has been partitioned into 98 collapsed strata with 3
PSUs per stratum. All PSUs are treated as sampled with replacement within
their respective strata. This method will provide somewhat conservative
standard errors, and this standard error estimator itself has less stability
than the standard error estimator described by Method 2.96 below.
Coding required, (SAS code provided):
STRATUM = INT(STRAT96/10) * 10 ;
PSU = PANEL ;
Note, INT ( ) is the Integer-value SAS function, e.g., INT(2.3) = 2
As a check the user should observe 98*3 = 294 PSUs when using the full
database.
For the above simplification of the NHIS sample design structure, the
following SUDAAN design statements may be used. (Note, the input file must
first be sorted by STRATUM and PSU variables).
PROC ... DESIGN = WR;
NEST STRATUM PSU ;
WEIGHT WTF;
Method 2.96 - Multiple PSUs per Stratum design sampled with replacement
This method provides for more statistically efficient variance estimation than
Method 1.96, since it makes better use of the sampling design information.
Its application is limited to software that can handle multiple PSUs per
stratum, e.g., SUDAAN. For this method the original certainty PSUs are
partitioned by aggregations of the original race-ethnic density strata used in
sampling. The first randomly sampled unit is actually the SSU variable which
is now treated as the PSU variable. (Note, a certainty PSU unit contributes
nothing to the variance at the PSU sampling level). Non-certainty strata
PSUs are treated as being sampled with replacement within their respective
strata.
Coding required (SAS code provided):
IF NSR96 = 1 THEN DO; /*1996 certainty strata PSUs */
STRATUM = STRAT96*100 + SUB_V;
PSU = SSU
END;
ELSE DO; /* 1996 non-certainty PSU */
STRATUM = STRAT96 ;
PSU = PSU96 ;
END;
As a check, the user should observe the following counts:
Certainty Strata PSUs 1736
Non-certainty Strata PSUs 240
Total PSUs 1976
For the Method 2.96 design structure, the following SUDAAN design statements
may be used. (Note, the input file must first be sorted by STRATUM and PSU
variables.)
PROC ... DESIGN = WR;
NEST STRATUM PSU ;
WEIGHT WTF ;
Caution. Both Method 1.96 and Method 2.96 should only be used on a full sample
person database. Using this method with subsetted data may lead to incorrectly
computed standard errors. (See the section Subsetted Data Analysis in the
1995 section). If using a subsetted data set, the user should check the degree
of agreement in the PSU counts with the values presented above for either of
the two methods. Unlike Method 1 for 1995, Method 1.96 is not robust for
analyzing subsetted survey data.
CAUTION
A typically used rule-of-thumb for degrees of freedom to associate with a
standard error is the quantity (number of PSUs - number of strata). This rule
assumes that the PSUs are somewhat comparable in size. For Method 2.96 this
rule may be grossly inaccurate since the concept of PSU is quite different for
certainty and non-certainty strata. Certainty strata PSUs of Method 2.96 have
small weighted values relative to those of non-certainty PSUs. The rule-of-
thumb degrees of freedom for Method 1.96 is 196, and Method 2.96 should
have a true degrees of freedom exceeding that of Method 1.96. However, for
practical purposes, any degrees of freedom exceeding 120 can be treated as
infinite, i.e., one uses a normal Z-statistic instead of a t-statistic for
testing. Note, that a one-tailed critical t0.025 at 120 degrees of freedom
is 1.98 while at an infinite degrees of freedom (i.e., a z-value) is 1.96. If
a variable of interest covers most of the NHIS PSUs, the limiting value would
probably be adequate for analysis. The user should consult a mathematical
statistican for discussion of degrees of freedom.
The observant reader may notice that the 1996 method 1.96 has a larger rule of
thumb degrees of freedom than the corresponding 1995 method 1. The 1996
variance estimation design consists of collapsed strata that may introduce a
much larger stratum-collapse bias than occurred in 1995, and furthermore, the
PSUs within each 1996 collapsed stratum have greater PSU weight diversity
than in 1995 which may reduce stability.
The section on SUBSETTED DATA ANALYSES in the 1995 section should be read
considering the changes provided in this 1996 section.