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NAEP Technical DocumentationStratification of Schools for the 2009 Twelfth-Grade Public School National Assessment
Stratification for the overall national grade 12 public school assessments was carried out via two distinct processes. First, the 11 state-assessment states were stratified by state and then stratified within state, as described in the state assessment stratification of schools.
The remainder of this section describes the stratification for the complement states frame: the 39 states plus the District of Columbia that were not part of the twelfth-grade state assessment in 2009. All stratification within these states was implicit. This implicit stratification of twelfth-grade public schools involved many dimensions and was serpentine. The first three dimensions in the stratification hierarchy were as follows:
- urbanization classification, and
- race/ethnicity status.
The New England and Mid-Atlantic census divisions were collapsed into a single stratum comprising the census region Northeast, as Connecticut, Massachusetts, New Hampshire, and New Jersey were all in the twelfth-grade public school state assessment. The remaining census divisions were not collapsed.
The urbanization strata within the census division strata were defined based on the urban-centric locale classification from the Common Core of Data (CCD).
The starting point for an urbanicity stratum then was the 12 urbanicity cells generated by the four primary urbanicity classifications and the three subclassifications within each primary classification within each census division stratum. Any urbanization cell with an expected sample size of fewer than four schools was combined with a neighboring urbanization cell within the same census division. Collapsing was first done among the subclassifier cells within the primary urbanicity classifications (subcell 1 collapsed with subcell 2, subcell 3 collapsed with subcell 2, subcell 2 collapsed with the smaller of subcells 1 and 3; if still too small, collapsing was done to the primary urbanicity level).
If a collapsed primary urbanicity level still had an expected school sample size of less than 4, then it was collapsed with a neighboring primary urbanicity level (1-City with 2-Suburbs first, 3-Urban Cluster with 4-Rural first, or all four together if necessary), all within each census division stratum. No collapsing across census division strata was necessary.
The final result of this was a set of census division-urbanicity strata with all strata having expected school sample sizes greater than 4.0.
The next step in the process was to divide the urbanicity strata into race/ethnicity strata. The first division was a dichotomization of each urbanicity stratum into a low and a high Black/Hispanic stratum (the cutoff was 15 percent Black and Hispanic students). If the expected school sample size of resultant strata was less than 8.0, then this was the final urbanicity-race/ethnicity stratum. If the expected school sample size exceeded 8.0, a further division was made.
For the low Black/Hispanic stratum, there were only five urbanicity strata that had a large enough expected school sample size, and these were dichotomized by state. The table below describes the dichotomization.
| Census division stratum | Urbanicity stratum | Group 1 states | Group 2 states |
|---|---|---|---|
| SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2009 Assessment. | |||
| Northeast region | Suburbs | Maine, New York | Pennsylvania, Rhode Island, Vermont |
| East North Central division | Suburbs | Indiana, Michigan | Ohio, Wisconsin |
| East North Central division | Towns | Indiana, Michigan | Ohio, Wisconsin |
| East North Central division | Rural distant | Indiana, Michigan | Ohio, Wisconsin |
| West North Central division | Rural remote | Kansas, Minnesota, Missouri | Nebraska, North Dakota |
Within the high Black/Hispanic stratum, the number of substrata was based on the expected school sample size. If the expected sample size was between 8.0 and 12.0, there were two substrata; if the expected sample size was between 12.0 and 16.0, there were three substrata; and if the expected sample size was over 16.0, there were four substrata.
The substrata were defined by percent Black and Hispanic students, with the cutoffs for substrata defined by weighted percentiles (with the weight equal to expected hits for each school). For two substrata, the cutoff was the weighted median; for three substrata, the weighted 33rd and 67th percentiles; for four substrata, the weighted median and quartiles.
The implicit stratification within these census division-urbanicity-race/ethnicity status strata was based on school type (public, BIE, (DoDEA)) and median income of the ZIP code area containing the school.
Last updated 25 February 2016 (GF)