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NAEP Weighting Procedures → 2002 Weighting Procedures and Variance Estimation → National Main Assessment Weights → Computation of Base Weights → Computation of New-School Base Weights

NAEP Technical DocumentationComputation of New-School Base Weights

			Trimming of School Base Weights

New schools had two components of their probability of selection: the probability of selection of their district into the new-school district sample, and the probability of selection of the new school into the sample given their district was canvassed. It should be noted that only public schools had new-school selection: private schools had no new-school selection. The web pages New-School Selection for Fourth and Eighth Grade Public Schools and New-School Selection for Twelfth- Grade Public Schools discuss new-school selection for fourth and eighth grades, and twelfth grades, respectively. In some cases the district probability of selection resulted in a very small probability of selection for the new school, even though enrollment in the new school may not be small. For this reason the new school's weight was trimmed if it was more than three times larger than what it would have been if it had been in the Common Core of Data (CCD) school sample, so that the new school and its weight would not contribute excessively to the mean square error.

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