NAEP Technical DocumentationSample Design for the 2015 National Assessment

			Fourth- and Eighth-Grade Public School National Assessments Twelfth-Grade Public School National Assessment Private School National Assessment

The 2015 national assessment included operational assessments in mathematics, reading, science, and vocabulary in public and private schools at grades 4, 8, and 12. In addition, a national special mathematics assessment was conducted in both public and private schools at grades 4 and 8, but not at grade 12.

The sample designs aimed to achieve nationally representative samples of students in the defined populations who were enrolled at the time of assessment.  

The samples were based on a two-stage sample design:

• selection of schools within strata; and
• selection of students within schools.

The samples of schools were selected with probability proportional to a measure of size based on the estimated grade-specific enrollment in the schools.

For fourth- and eighth-grade public schools, the aggregate of the NAEP state student samples and assessments in mathematics, reading, and science constitute the corresponding NAEP national student samples and assessments. The vocabulary and special national mathematics assessments consisted of a nationally representative subsample of schools from the state school samples.

Nationally representative samples were drawn for the private school students in grades 4, 8, and 12 and for the public school students in grade 12.

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