NAEP Technical DocumentationSchool Sample Selection for the 2017 State Assessment

			Computation of Measures of Size School Sample Sizes: Frame and New School Evaluation of the Samples Using State Achievement Data

For the grades 4 and 8 public school state assessment samples, schools were sampled independently from each jurisdiction with probability proportional-to-size (PPS) using systematic sampling. Prior to sampling, schools in each jurisdiction were sorted by the appropriate implicit stratification variables (urbanicity status, race/ethnicity status, and achievement score or zip code-based median household income or estimated grade enrollment) in a serpentine order. A school's measure of size was a complex function of the school's estimated grade enrollment. Schools whose measure of size was larger than the sampling interval could be selected or “hit” multiple times. Schools with multiple hits were selected with certainty and had larger student sample sizes.

The sampled schools for the public school state assessment samples came from two frames: the public school sample frame (as constructed from the Common Core of Data [CCD]) and the new-school sampling frame.

For the CCD-based frame, schools were sampled at a rate that would yield specific target student sample sizes for each jurisdiction. At grades 4 and 8, jurisdictions had a target assessed student sample size of 5,400 students: 2,700 students each for the reading and mathematics operational assessments. The special mathematics assessment in Puerto Rico had a target assessed student sample size of 6,000 students. By design, Bureau of Indian Education (BIE) schools were not part of the state assessments this year. However, separate BIE school samples were selected based on target student sample sizes that were large enough to ensure that BIE schools were sufficiently represented in the national samples.

The schools in the new-school frame were sampled at the same rate as the CCD-based school frame.

Prior to selection, schools were deeply stratified in each jurisdiction to ensure that the school sample distribution reflected the school population distribution as closely as possible, with regard to the stratification variables, to minimize sampling error. The success of this approach was shown by comparing the proportion of minorities enrolled in schools (based on CCD values for each school), median income, and urban-centric locale (viewed as an interval variable) reported in the original frame against the school sample.

In addition, the distribution of state assessment achievement scores for the original frame can be compared with that of the school sample for those jurisdictions for which state assessment achievement data are available, as was done in the evaluation of the samples using state achievement data.

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