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NAEP Technical DocumentationStratification of Private Schools for the 2011 Writing Computer-Based Assessment (WCBA)

Prior to stratification, the private school sampling frame was divided into grade-specific files, one each for eighth and twelfth grade. For each such grade-specific 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 (urban-centric locale), and
• estimated grade enrollment.

Schools in noncertainty PSUs were hierarchically sorted by

• PSU stratum,
• urbanization classification (urban-centric locale), and
• estimated grade enrollment.

 

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