What is the sample design?
In the United States, CivEd was administered to a representative sample of 2,811 students among 124 public and private schools at the beginning of ninth grade, the grade in which most 14-year-olds were enrolled at the time of the assessment (October 1999). The overall sample design was intended to approximate a self-weighting sample of students as much as possible, with each ninth-grade student in the United States having an approximately equal probability of being selected within the major school strata. Thus, the results of CivEd are based on a representative sample of students. Each selected school that participated in the study, and each student assessed, represents a portion of the population of interest. As a result, after adjustments for student and school non-responses, the findings presented are representative of all ninth-graders in the nation.
