NAEP Assessment Sample Design → NAEP 2009 Sample Design → Sample Design for the 2009 National Assessment → Hands-On Tasks (HOT) and Interactive Computer Tests (ICT) for the 2009 Science Assessment → Selection of Primary Sampling Units (PSUs) for the 2009 Science HOT and ICT Assessments → Final Primary Sampling Unit (PSU) Sample

NAEP Technical DocumentationFinal Primary Sampling Unit (PSU) Sample

For the science hands-on tasks (HOT) and interactive computer tests (ICT) assessments, a primary sampling unit (PSU) sample was drawn independently from each of the 76 noncertainty strata defined in Final Primary Sampling Unit Strata. The 76 noncertainty strata were then paired and one stratum from each of the 38 pairs was randomly selected. One PSU was selected with probability proportionate to size (with size equal to estimated number of youths) within each stratum. PSUs were selected from only 38 strata rather than 76 because the relatively small size of these student samples made it more cost-effective to use fewer PSUs. The selection of the noncertainty PSUs was designed to minimize the overlap with the 2008 Arts sample.

Also, 29 PSUs were included in the sample of PSUs with certainty.

Distribution of sampled PSUs for science assessment, by PSU type: 2009

PSU type	Number of sampled PSUs
	SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2009.
Total	67
Census region
Northeast	10
Midwest	14
South	26
West	17
Certainty/metropolitan status
Certainty metropolitan	29
Noncertainty metropolitan	27
Noncertainty non-metropolitan	11

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