Table of Contents | Search Technical Documentation | References
NAEP Technical DocumentationMissing Stratification Variables for the 2024 State Assessment
Schools with missing stratification variables had their data
imputed as follows.
Schools missing the urbanicity (urban-centric locale) variable were assigned the modal value of urbanicity for schools in the same five-digit zip code or the same city. The modal value is the value that occurs the most. For example, one school in zip code 32305 has missing urbanicity. In the same five-digit zip code area, there are 20 schools with non-missing urbanicity variable. Fifteen of them have an urbanicity value of "mid-size city", and the other five have an urbanicity value of "large suburb". The modal value of urbanicity for schools in zip code 32305 is "mid-size city".
The mean ethnicity percentage was imputed at the five-digit zip code level only if all schools were missing ethnicity at the district level, and only at the three-digit zip code prefix if the five-digit zip code ethnicity mean was missing as well. Thus, schools with missing or questionable values in race/ethnicity enrollment data—those in which the summation of the ethnicity percentages did not fall in the range 97 through 103, indicating a gross error—were assigned the average race/ethnicity enrollment within (in priority order) their school district, five-digit zip code, or three-digit zip code prefix.
Schools with missing achievement data in jurisdictions and grades for which achievement data were used in stratification were assigned the mean achievement data value within their urbanicity and race/ethnicity classification. The achievement data were imputed only for those schools in jurisdictions and grades in which achievement data were used for stratification.
Schools missing median household income were assigned the mean value of median household income for the five-digit zip code prefix in which they were located. If it was not available or it was unreliable, then the mean value of median household income for the three-digit zip code prefix was used. In some cases, imputation was not possible at the three-digit zip code level, and needed to be done at the city and state level.
Schools with missing estimated grade enrollment had their estimated grade enrollment set to 20.
Last updated 24 November 2025 (SK)