NAEP Technical Documentation2019 Fourth- and Eighth-Grade Public School National Science Assessment

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

The fourth- and eighth-grade public school samples for the national science assessments were designed to produce nationally representative samples of students enrolled in fourth and eighth grades in public schools in the United States and to accommodate the administration of the assessment in two modes: digitally based assessment (DBA) on tablets and paper-based assessment (PBA) using paper and pencil.

The target sample sizes for the public school science sample were 25,200 (17,100 DBA and 8,100 PBA) assessed students at grade 4 and 26,100 (17,100 DBA and 9,000 PBA) at grade 8. Prior to sampling, the target sample sizes were adjusted upward to offset expected school and student attrition due to nonresponse and ineligibility.

Samples were selected using a two-stage probability-based design that involved selection of schools from within strata and selection of students within schools. The first-stage samples of schools were selected with probability proportional to a measure of size based on estimated grade-specific enrollment in the schools.

The sampling of students at the second-stage involved three steps: (1) sampling of students in the targeted grade (fourth or eighth) from each sampled school, (2) assignment of assessment mode (DBA or PBA), and (3) assignment of assessment subject (science) to the sampled students.

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