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NAEP Technical DocumentationStratification of Private Schools in the 2012 Economics Assessment

Prior to stratification, the private school sampling frame was divided into a grade-specific file for grade 12. For the grade 12 file, schools were explicitly stratified by private school affiliation (Catholic, non-Catholic, and unknown affiliation). Private school affiliation was unknown for nonrespondents to the NCES Private School Universe Survey (PSS). Within private school type, separate implicit stratification schemes were used to sort schools in certainty primary sampling units (PSUs) and noncertainty PSUs. In all cases, the implicit stratification was achieved via a "serpentine sort."

Within each certainty PSU, the schools were hierarchically sorted by

• census region;
• urbanization classification (based on urban-centric locale); and
• estimated twelfth-grade enrollment.

Schools in noncertainty PSUs were hierarchically sorted by

• PSU stratum;
• urbanization classification (based on urban-centric locale); and
• estimated twelfth-grade enrollment.

 

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