The sample for the 2001 national main assessment in geography and U.S. history was a multistage probability-based sample. This was a national sample in which counties or groups of counties, also known as primary sampling units (PSUs), were the first-stage sampling units, and elementary and secondary schools were the second-stage units. The third stage of sampling consisted of the assignment of sample types to sampled schools. The fourth and final stage involved selection of students within schools and their assignment to session types (geography or U.S. history).
The 2001 sample design oversampled specific student groups to enhance the reliability of NAEP estimates for the following groups:
The oversampling of these groups was achieved at either the school or student sampling stages and, in the case of Black and Hispanic students, at both stages. In addition, the 2001 national main samples included substitute schools to compensate for school-level nonresponse and to improve the overall number of assessed students.
A total of 94 PSUs were included in the sample. The sample of schools that participated in the assessment included 370 schools at the fourth-grade level, 370 schools at the eighth-grade level, and 370 schools at the twelfth-grade level. Assessments were administered in these schools to 15,700 fourth-graders, 22,700 eighth-graders, and 21,800 twelfth-graders for a total of 60,200 assessed students overall.