NAEP Technical Documentation2020 Private School Long-Term Trend Assessment

			Target Population Sampling Frame Stratification of Schools Sampling of Schools Substitute Schools Ineligible Schools Student Sample Selection

The NAEP 2020 sample design yielded nationally representative samples of private school students at ages 9 and 13 for long-term trend (LTT) through a three-stage approach:

• selection of primary sampling units (PSUs);
• selection of schools within strata; and
• selection of students within schools.

The sample of schools was selected with probability proportional to a measure of size based on the estimated age enrollment in the schools.

The 2020 sampling plan was designed to assess 1,600 students (800 for each of the two age-specific samples) in private schools, for LTT. These students were allocated among tests in mathematics and reading. Target sample sizes were adjusted to reflect expected private school and student response and eligibility.

Schools on the sampling frame were explicitly stratified prior to sampling by private school affiliation (Catholic, non-Catholic, and unknown affiliation). Within affiliation type, schools were implicitly stratified by PSU type (certainty/noncertainty). In certainty PSUs, further stratification was by census region, urbanization classification, and estimated age enrollment. In noncertainty PSUs, additional stratification was by PSU stratum, urbanization classification, and estimated age enrollment.

From the stratified frame of private schools, systematic random samples of age-eligible schools were drawn with probability proportional to a measure of size based on the estimated age enrollment of the school in the relevant age.

Each selected school in the private school sample provided a list of eligible enrolled students from which a systematic, equal probability sample of students was drawn.

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