Task 3: How to Consult the Documentation
Before analyzing the data, you will need to know how the variable is coded, data editing, processing, and collection information, and the frequency (or sample size) of the variable. This information is found in the documentation for the components:
In the data files for NHANES 1999-2000 and NHANES 2001-2002, the frequency file is a separate piece of documentation. However, in NHANES 2003-2004 documentation, the frequency counts are included in the codebook.
Step 1: Codebook
First, you will check the demographics codebook to learn how the gender variables, RIAGENDR, is coded in NHANES data.
If you are still at the PDF file of the variable list, click your browser's Back button twice to return to the NHANES 2001-2002 page. If you returned to the NHANES homepage, click the Datasets and Related Documentation link, then click the NHANES 2001-2002 link.
Click the Demographics link, then Codebook link. The codebook is an Adobe Acrobat PDF file and you can search for the variable, in this case RIAGENDR, and learn how the variable's values are coded, the target population, SAS label, and if the variable was part of a skip pattern. (In NHANES 2003-2004, the frequency counts were also included.)
You should check the codebooks of the other components on your own.
Step 2: Data file documentation
Now, you will check the laboratory data file documentation to determine which data file to use in your analysis — Lab 13 or Lab 40.
If you are still at the PDF file of the demographic codebook, click your browser's Back button twice to return to the NHANES 2001-2002 page. If you returned to the NHANES homepage, click the Datasets and Related Documentation link, then click the NHANES 2001-2002 link.
Click the Laboratory link, then the Lab 13 Total Cholesterol and HDL Cholesterol Doc link. The documentation is an Adobe Acrobat PDF file and you can search it for the variables "LBXTC," one of the cholesterol variables you identified in the previous task. As you read the notes for each variable, you will find that LBXTC from Lab 13 is the appropriate variable to use in your analysis.
If you wish, go back to the 2001-2002 Laboratory files and open the data file documentation for Lab 40, search for the other cholesterol variable, "LBXSCH," and confirm that it is not the variable to use by reading the analytic notes.
The self-guided activity is to locate and read the data file documentation for the other variables in your analysis — blood pressure examination, blood pressure questionnaire, and demographics.
Step 3: Frequency tables
Finally, you will check the frequency table for the gender variable, RIAGENDR from the demographics component, to determine the sample size.
If you are still at the PDF file of the data file documentation, click your browser's Back button twice to return to the NHANES 2001-2002 page. If you returned to the NHANES homepage, click the Datasets and Related Documentation link, then click the NHANES 2001-2002 link.
Click the Demographics link, then the Freqs link. The frequency table is an Abode Acrobat PDF file and on the left side you will see a list of bookmarks labeled with variable names. Find the gender variable, RIAGENDR, in this list and click it. The PDF file advances to the page with the RIAGENDR frequency counts for the possible responses to the question. Use the final row in the Cumulative Frequency column as your sample size.
Close Window to return to module page.