NAEP Technical DocumentationStratification by Race/Ethnicity Classification

Race/ethnicity classification was based on the two largest racial/ethnic percentages (among Black, Hispanic, Asian, American Indian, and non-Hispanic White students) within each urbanization group within a jurisdiction. The largest race/ethnicity group (either the majority of the population or the plurality of the population, that is, the largest group where there is no majority) by definition was set aside. Within each of these cells, the largest race/ethnicity group, expressed as a percentage (excluding the majority or plurality), and the second largest race/ethnicity group, as a percentage, and the racial/ethnic groups to which they belonged were identified. Three different race/ethnicity classification schemes were used, as follows:

Case 1: Urbanization classifications with less than 7 percent of students in the largest race/ethnicity group were not stratified by race/ethnicity enrollment (race/ethnicity stratification value 0). There were no race/ethnicity strata within these domain-urbanicity cells (i.e., only one stratum was used for the domain-urbanicity cell).

Case 2: Urbanization classifications with greater than or equal to 7 percent of students in the largest race/ethnicity but with no more than one race/ethnicity with 15 percent or more of the population were stratified by ordering the sum of the percent race/ethnicity enrollment for the largest and next largest race/ethnicity within the urbanization classification and dividing the schools into three groups with approximately equal numbers of students per racial/ethnic classification.

Case 3: In urbanization classifications with greater than 15 percent of students in both the largest and next largest racial/ethnic groups, race/ethnicity classifications were formed with the objective of providing equal strata with emphasis on the two largest racial/ethnic groups. The stratification was performed as follows: The largest racial/ethnic group provided the primary stratification variable; the second largest racial/ethnic group provided the secondary stratification variable. Within urbanization classification, the schools were first sorted based on the primary stratification variable. Then they were divided into two groups of schools containing approximately equal numbers of students based on estimated grade enrollment. Within each of these two groups, the schools were sorted by the secondary stratification variable and subdivided into two subgroups of schools containing approximately equal numbers of students. As a result, within urbanization classification there were four race/ethnicity classifications (e.g., low primary variable/low secondary variable, low primary variable/high secondary variable, high primary variable/low secondary variable, and high primary variable/high secondary variable).

Last updated 14 July 2009 (JL)

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