NAEP Technical DocumentationFinal Primary Sampling Unit (PSU) Strata for the 2018 Assessment

			Stratification for Northeast metropolitan noncertainty primary sampling units Stratification for Northeast non-metropolitan noncertainty primary sampling units Stratification for Midwest metropolitan noncertainty primary sampling units Stratification for Midwest non-metropolitan noncertainty primary sampling units Stratification for South metropolitan noncertainty primary sampling units Stratification for South non-metropolitan noncertainty primary sampling units Stratification for West metropolitan noncertainty primary sampling units Stratification for West non-metropolitan noncertainty primary sampling units

The strata were defined using the selected stratifiers from the stepwise regression analysis (see Stepwise Regression Analysis Results for PSU Stratification). The cutoffs were selected so that roughly equal measures of size were represented by each stratum.

The number of stratifiers used to define the noncertainty PSU strata within each primary stratum ranged from 1 to 5 stratifiers depending on the size of the primary stratum. For instance, the Northeast non-metropolitan primary stratum, which had about 1 million youths in noncertainty PSUs, used only one stratifier; whereas the South metropolitan primary stratum had about 13 million youths in noncertainty PSUs and used five stratifiers.

The final noncertainty PSU strata are presented in summary tables for each primary PSU stratum. The tables show the definition, number of PSUs, and size of each stratum.

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