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About the Assessment: Target Population and Sample Size

The schools and students participating in NAEP assessments are selected to be representative of all schools nationally and of public schools at the state level. Samples of schools and students are drawn from participating states and from the District of Columbia and Department of Defense schools.  While results for students assessed in Alaska, the District of Columbia, Kansas, Nebraska, and Vermont contributed to the results for the nation at grades 4 and 8, sample sizes were not large enough to report results for these states/jurisdictions separately. At grades 4 and 8, the results from the assessed students are combined to provide accurate estimates of the overall performance of students in the nation and in individual states and other jurisdictions. States with districts participating in the Trial Urban District Assessments have larger sample sizes.

While national results reflect the performance of students in both public schools and nonpublic schools (i.e., private schools, Bureau of Indian Education schools, and Department of Defense schools), state-level results reflect the performance of public school students only. Results are reported separately for Department of Defense schools in state tables and maps. More information on sampling can be found in NAEP Technical Documentation.

The sample of students in the participating TUDA school districts is an extension of the sample of students who would usually be selected by NAEP as part of state and national samples. Results for students in the TUDA samples are also included in state and national samples with appropriate weighting. For example, the results reported for students in Boston also contribute to the results reported for Massachusetts and to the results for the nation.

National and State
Student sample sizes and target populations in NAEP science at grade 12, by type of school: 2009
Type of School Sample size Target population
    Nation 11,500 3,214,000
Public 10,300 2,941,000
Private 1,200 273,000
NOTE: The sample size is rounded to the nearest hundred. The target population is rounded to the nearest thousand. Data for BIE and DoDEA schools are counted in the overall nation total, but not in the nation (public) total. Detail may not sum to totals because of rounding.
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2009 Science Assessment.