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Map It
A feature in American FactFinder which allows the user to preview a geographic area on a reference map before selecting it.

Margin of error (MOE)
A margin of error is the difference between an estimate and its upper or lower confidence bounds. Confidence bounds can be created by adding the margin of error to the estimate (for an upper bound) and subtracting the margin of error from the estimate (for a lower bound). All published margins of error for the American Community Survey are based on a 90 percent confidence level.

Related terms:
Confidence interval (American Community Survey), Lower bound (American Community Survey), Upper bound (American Community Survey)

Marital status
Adults are generally classified by marital status as being married, never married, separated, divorced or widowed.

Mean
This measure represents an arithmetic average of a set of numbers. It is derived by dividing the sum of a group of numerical items by the total number of items in that group. For example, mean family income is obtained by dividing the total of all income reported by people 15 years and over in families by the total number of families.

Related term:
Derived measures

Mean income
Mean income is the amount obtained by dividing the total income of a particular statistical universe by the number of units in that universe. Thus, mean household income is obtained by dividing total household income by the total number of households. For the various types of income, the means are based on households having those types of income.

Related term:
Income

Median
This measure represents the middle value (if n is odd) or the average of the two middle values (if n is even) in an ordered list of data values. The median divides the total frequency distribution into two equal parts: one-half of the cases fall below the median and one-half of the cases exceed the median.

Related term:
Derived measures

Median age
This measure divides the age distribution in a stated area into two equal parts: one-half of the population falling below the median value and one-half above the median value.

Related term:
Age

Median income
The median income divides the income distribution into two equal groups, one having incomes above the median, and other having incomes below the median.

Related term:
Income

Metadata
Information about the content, quality, condition, and other characteristics of data.

Metadata related to tables presented in American FactFinder can be found by clicking on column headings or by clicking "Help" and then "Census Data Information."

Metropolitan
Refers to those areas surrounding large and densely populated cities or towns.

Metropolitan Area (MA)
A collective term, established by the federal Office of Management and Budget, to refer to metropolitan statistical areas, consolidated metropolitan statistical areas, and primary metropolitan statistical areas.

Metropolitan statistical area (MSA)
A geographic entity defined by the federal Office of Management and Budget for use by federal statistical agencies, based on the concept of a core area with a large population nucleus, plus adjacent communities having a high degree of economic and social integration with that core. Qualification of an MSA requires the presence of a city with 50,000 or more inhabitants, or the presence of an Urbanized Area (UA) and a total population of at least 100,000 (75,000 in New England). The county or counties containing the largest city and surrounding densely settled territory are central counties of the MSA. Additional outlying counties qualify to be included in the MSA by meeting certain other criteria of metropolitan character, such as a specified minimum population density or percentage of the population that is urban. MSAs in New England are defined in terms of minor civil divisions, following rules concerning commuting and population density.

Related terms:
Consolidated metropolitan statistical area (CMSA), Primary metropolitan statistical area (PMSA)

Microdata files
Files with non-aggregated data about the units sampled. For surveys of individuals, microdata files contain records for each individual interviewed; for surveys of organizations, the microdata contain records for each organization.

To ensure confidentiality, the Census Bureau publishes microdata only after it is stripped of all identifying information.

Migration
Migration includes all changes of residence including moving into, out of, or within a given area. Foreign country, or state, county and city of previous residence is collected and coded. In 12 states, minor civil division (MCD) is also coded.

International Migration
Movement of people across international borders.

Related terms:
Immigrants, Residence 5 years ago

Mining areas
A set of boundaries available in Reference Map that focus on geographies relevant to the census of mineral industries within the Economic census.

Related term:
Reference map

Minor civil division (MCD)
A primary governmental and/or administrative subdivision of a county, such as a township, precinct, or magisterial district. MCDs exist in 28 states and the District of Columbia.
In 20 states, all or many MCD's are general-purpose governmental units: Connecticut, Illinois, Indiana, Kansas, Maine, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, New Hampshire, New Jersey, New York, North Dakota, Ohio, Pennsylvania, Rhode Island, South Dakota, Vermont, and Wisconsin. Most of these MCD's are legally designated as towns or townships.

Related Terms:
Census county division (CCD), County subdivision, Unorganized territory

Mortgage status
"Mortgage" refers to all forms of debt where the property is pledged as security for repayment of the debt, including deeds of trust, trust deed, contracts to purchase, land contracts, junior mortgages, and home equity loans.

Multi-unit structure
A building that contains more than one housing unit (for example, an apartment building).

Municipio
Primary legal divisions of Puerto Rico. These are treated as county equivalents.

Related term:
County and equivalent entity