NAEP Assessment Sample Design → NAEP 2012 Sample Design → 2012 Long-Term Trend (LTT) Assessment Sample Design → 2012 Private School Long-Term Trend (LTT) Assessment → Stratification of Private Schools in the 2012 Long-Term Trend (LTT) Assessment

NAEP Technical DocumentationStratification of Private Schools in the 2012 Long-Term Trend (LTT) Assessment

Prior to stratification, the private school sampling frame was divided into age-specific files, one each for ages 9, 13, and 17. For each age-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 (based on urban-centric locale); and
• estimated age-specific enrollment.

Schools in noncertainty PSUs were hierarchically sorted by

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

 

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