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NAEP Sample Design → NAEP 2005 Sample Design → State Assessment Sample Design → Stratification of Schools in the 2005 State Assessment → Stratification Variables → Stratification by Achievement Data and Median Income

NAEP Technical DocumentationStratification by Achievement Data and Median Income

			Jurisdictions Using Achievement Data or Median Household Income in Stratification

The achievement data are derived from the results of state assessment programs which were obtained from each jurisdiction. The contents of the achievement data files varied by jurisdiction and included achievement measures for a variety of subjects, grades, and multiple assessment programs. One achievement measure was selected for each responding jurisdiction to be used in the stratification process. Where available, the achievement data were used for implicit stratification by grade. Since the achievement data are more current than the median household income data, as well as more likely to be well-correlated to NAEP assessment scores, they were judged to be a more effective stratification variable. The achievement measures were selected according to the following criteria:

• Achievement measures from state assessments conducted in mathematics, science, and reading (in that order of priority) were utilized, if available. For grade 4, data from fourth-grade assessments, if available; otherwise, data from third-grade assessments. For grade 8, data from eighth-grade assessments if available; otherwise, data from seventh-grade assessments. For both grades, data from 2003 assessments (the latest available) were preferred; 2002 or 2001 assessments were used as secondary choices. In one case, 1997–98 results were used as the latest available.

• Achievement measures should match to at least 70 percent of the schools on the sampling frames.

• Achievement measures should differentiate schools from one another. For example, district-level measures, measures with high missing rates or pass/fail indicators were judged not to be good differentiators. In addition, achievement measures that did not have good dispersion were not used for stratification.

• All other things being equal, the priorities for score types were average scale score, median scale score, percentile rank, median percentile rank, normal curve equivalent, raw score, index score, and percentage above a particular cut-point, quartile or nine-point scale. In general, only one or two of these score types were available for any given state/grade/subject/year.

Achievement data useful for implicit stratification were obtained from 45 of 64 participating jurisdictions. Where achievement data were not used, median household income from the 2000 Census was used.

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