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NAEP Sample Design → NAEP 2002 Sample Design → 2002 State Assessment Sample Design → Stratification of Schools in Public School Sampling Frame → Stratification Variables for the 2002 State Assessment

NAEP Technical DocumentationStratification Variables for the 2002 State Assessment

			Urban Classification Minority Classification Achievement Score and Median Income Missing Stratification Variables

The stratification of public schools involved four dimensions. Public schools were stratified hierarchically by

• small or large district status,
• urbanization classification,
• minority classification, and
• achievement score or median income of zip code.

District status is defined based on whether or not the school’s district has 20 percent of the jurisdiction’s population. The urbanization classification classifies schools by location (e.g., whether the school is in a center of a city, in an urban fringe of a city, in a town, or in a rural area), and also classifies as to the size of city (large or medium), town (large or small), and whether a rural area is in a metropolitan statistical area (or not).

Minority classification sorts schools based on whether or not they have high percentages of minorities which are predominant in particular jurisdictions. Minorities are defined as

• Black students,
• Hispanic students,
• Asian-American and Pacific Islander students, and
• American Indian students.

These minorities are nested within each cell defined by the urbanization classification (within each jurisdiction). Jurisdiction-urbanization cells with no predominant minorities (less than 7 percent for every minority) have no minority classifications. Jurisdiction-urbanization cells with two predominant minorities (greater than 20 percent for at least two minorities) have four minority cells based on percentages of the prevalent minorities. Jurisdiction-urbanization cells with only one predominant minority (one minority greater than 7 percent, and no more than one minority greater than 20 percent) have three minority cells based on the sum of the percentages of the prevalent minorities.

The last stratification variable is achievement score or median household income. Achievement data were used, if they were available, for a particular jurisdiction and grade. If achievement data were not available, median household income of the ZIP Code area where the school was located was used (obtained from the 1990 Census and compiled from Donnelly Marketing Information Systems).

The implicit stratification in this four-fold hierarchical stratification was achieved via a "serpentine sort." This stratification was accomplished by alternating between ascending and descending sort order on each variable successively through the sort hierarchy. Within this sorted list, the schools were sorted, in serpentine order, by achievement data or median household income, within each cell determined by the three higher classifications (district status, urbanization classification, minority classification), with ascending order for achievement data/median household income used in every other cell, and descending order for achievement data/median household income used in the remaining cells, giving an ascending-descending-ascending-descending pattern. The district status, urbanization classification, and minority classification cells were also sorted in serpentine order. Within each urbanization classification, minority classification cells are sorted by ascending order for one urbanization classification, followed by descending order for the next urbanization classification, and so on. Likewise, urbanization classification cells are sorted by ascending order within the first district status cell, by descending order within the second district status cell, and so on.

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