NAEP Technical DocumentationSubstitute Private Schools for the 2012 Long-Term Trend (LTT) Assessment

Substitutes were preselected for the private school samples by sorting the school frame file according to the actual order used in the sampling process (the implicit stratification). For operational reasons, the original selection order was embedded within the sampled primary sampling unit (PSU) and state. Each sampled school had each of its nearest neighbors within the same sampling stratum on the school frame file identified as a potential substitute. Since age-specific enrollment was used as the last sort ordering variable, the nearest neighbors had age-specific enrollment values very close to that of the sampled school. This was done to facilitate the selection of about the same number of students within the substitute as would have been selected from the original sampled school.

Schools were disqualified as potential substitutes if they were already selected in any of the original private school samples or assigned as a substitute for another private school (earlier in the sort ordering). Schools assigned as substitutes for age seventeen schools were disqualified as potential substitutes for age nine and age thirteen schools, and schools assigned as substitutes for age thirteen schools were disqualified as potential substitutes for age nine schools.

If both nearest neighbors were still eligible to be substitutes, the one with a closer age-specific enrollment was chosen. If both nearest neighbors were equally distant from the sampled school in their age-specific enrollment (an uncommon occurrence), one of the two was randomly selected.

Of the 360 original sampled private schools for the long-term trend (LTT) assessment, 107 schools had substitutes activated when the original eligible schools did not participate. Ultimately, 43 of the activated substitute private schools participated.

Last updated 05 June 2013 (JL)

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