​​​​​NAEP Technical Documentation2022 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 2022 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 2022 sampling plan was designed to assess 1,640 students in private schools for LTT at each age. 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 for​ the relevant age. The measures of size included an adjustment made in an attempt to ensure the inclusion of all eligible schools that were part of the 2020 private school long-term trend sample for ages 9 and 13. The NAEP sampling procedures used an adaptation of the Keyfitz process to compute conditional measures of size that, by design, maximized the overlap of schools selected for both the 2020 and 2022 long-term trend ​assessments at each 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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