NAEP Technical DocumentationPrimary Sampling Unit Generation: Metropolitan Statistical Areas

The Office of Management and Budget Consolidated Metropolitan Statistical Areas (CMSAs) were used to define primary sampling units (PSUs) in Metropolitan Statistical Areas (MSAs) where these were defined (e.g., New York-Northern New Jersey-Long Island NY-NJ-CT-PA CMSA), and otherwise Metropolitan Statistical Areas (MSAs) or New England County Metropolitan Areas (NECMAs) were used. All CMSAs, MSAs, and NECMAs were split along state boundaries.¹ The PSUs were generally the portions of CMSAs, MSAs, and NECMAs within individual states (called 'proto-PSUs'). For example, the New York-Northern New Jersey-Long Island NY-NJ-CT-PA CMSA was partitioned into four proto-PSUs by state.

If the proto-PSU did not violate the size constraints, it was defined as a PSU. In some cases, these proto-PSUs violated the minimum size constraint of 15,000 youths for the Northeast or Southeast regions, and 10,000 youths for the Central or West regions. There were 11 of these proto-PSUs violating size constraints, corresponding to 12 counties. In the four of these 11 cases where the size was close to the constraint, they were defined as PSUs. In the remaining seven smaller cases, the counties in question were added to the pool of non-MSA counties to be formed into non-MSA PSUs (see PSU generation: non-MSA PSUs).

A total of 17 of the newly-created PSUs were defined as certainty PSUs. The remaining 299 PSUs comprised the Metropolitan Statistical Area frame for PSU sampling, covering a total of 696 counties. The table below presents estimates for the number of youths by NAEP region (these estimates come from the county-level estimates of numbers of persons aged 0 to 17 from the 2000 Census Summary File 1 [SF-1] files).

Noncertainty Metropolitan Statistical Area (MSA) primary sampling unit frame, long-term trend assessment: By NAEP region, 2004
NAEP region	PSUs	Counties	Youths
Total	299	696	33,086,000
Northeast	40	87	4,934,000
Southeast	103	291	10,237,000
Central	82	195	8,669,000
West	74	123	9,248,000
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2004.

¹ Note that this is a change from earlier NAEP cycles. Field personnel had indicated that contacts with state officials were very important in the process of recruiting schools. Because of this it was decided that making single-state rather than multi-state PSUs was a better approach. In a few cases, small-size proto-PSUs were combined across state lines, if it was necessary to satisfy other criteria.

Last updated 10 June 2008 (GF)

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