NAEP Assessment Sample Design → NAEP 2011 Sample Design → Sample Design for the 2011 National Assessment → 2011 Writing Computer-Based Assessment (WCBA) → Private School 2011 Writing Computer-Based Assessment (WCBA)

NAEP Technical DocumentationPrivate School 2011 Writing Computer-Based Assessment (WCBA)

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

The NAEP 2011  writing computer-based assessment (WCBA) sample design yielded nationally representative samples of private school students in grades 8 and 12 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 grade enrollment in the schools.

The 2011 national WCBA sampling plan had a goal of assessing 2,200 eighth-graders and 2,200 twelfth-graders. 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, urban-centric locale, and estimated grade enrollment. In noncertainty PSUs, additional stratification was by PSU stratum, urban-centric locale, and estimated grade enrollment.

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

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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