A primary sampling unit (PSU) sample was drawn independently from each of the 76 noncertainty strata defined in Final Primary Sampling Unit Strata. One PSU was selected with probability proportionate to size (with size equal to number of youths) within each stratum. Also, 29 PSUs were included in the sample of PSUs with certainty.
|PSU type||Number of
|SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2006 .|