The national results presented on this website are based on nationally representative probability samples of twelfth-grade students. The sample was chosen using a stratified two-stage design that involved sampling students from selected schools (public and nonpublic) across the country.
Each selected school that participated in the assessment and each student assessed represents a portion of the population of interest. Sampling weights are needed to make valid inferences from the student samples to the representative populations from which they were drawn. Sampling weights account for disproportionate representation of students from different states and for students who attend nonpublic schools. Sampling weights also account for lower sampling rates for very small schools and are used to adjust for school and student nonresponse. See a table summarizing the participation rates for schools and students.
For the 2006 economics assessment, accommodations for students with disabilities (SD) and English language learners (ELL) were permitted for the entire sample of students. To learn more, read about the NAEP inclusion policy.