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NAEP Sample Design → Sample Design for the 2000 Assessment → National Main Assessment Sample Design in 2000 → Primary Sampling Units for the 2000 National Main Assessment → Sparsely Populated States in the 2000 National Main Assessment

NAEP Technical DocumentationSparsely Populated States in the 2000 National Main Assessment

Primary sampling units (PSUs) were formed and selected in six sparsely populated states in the grade 8 public school sample to improve the efficiency of the field operations. The basic grade 8 public school sample involved a stratified sample of schools, with state as the primary stratification, and an allocation of sampled schools to states proportionate to population size. If this design were applied to every state, only two or three schools would be assessed in states with the smallest populations. It would be extremely inefficient from a field operations point of view to assess unclustered samples of two or three schools in states such as Alaska and Wyoming, especially with the assessments taking place in February. In a few states, clustering the grade 8 public school sample in a few geographic PSUs, while increasing variance, did improve field work efficiency. Three PSUs were selected for the sample from PSUs formed in six sparsely populated states—Alaska, Idaho, Montana, North Dakota, South Dakota, and Wyoming.

Because the six states were from two NAEP regions, and as national main sample designs use region as the first stratification characteristic (and region is a primary reporting variable), it was important to have at least one PSU from each region. In other national samples, each noncertainty PSU represents approximately 0.8 percent of the U.S. population, and this seemed a reasonable guide for the amount that should be represented by each of the PSUs in this case.

For the sparsely populated states involved, North and South Dakota combined made up 0.53 percent of the U.S. population in 1992, while Alaska, Idaho, Montana, and Wyoming together made up 1.2 percent. On this basis, it was reasonable to select one PSU from the central NAEP region (North and South Dakota) and two from the west NAEP region (Alaska, Idaho, Montana, and Wyoming). Therefore there were a total three PSUs selected to represent sparsely populated states.

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