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NAEP Analysis and Scaling → Estimation of Population and Student Group Distributions → Examining the Population-Structure Models Used in NAEP → Proportion of Scale Score Variance Accounted for by the Population-Structure Models → Proportion of Scale Score Variance Accounted for by the Population-Structure Models, Reading Long-Term Trend Assessment, By Age: 2012
NAEP Technical DocumentationProportion of scale score variance accounted for by the conditioning model, reading long-term trend assessment, by age: 2012
Age Number of initial group-defining contrasts1 Number of principal components1  Proportion2 of scale score variance accounted for by the population-structure model
1 Excluding the constant term.
2 (Total Variance – Residual Variance)/Total Variance, where Total Variance consists of both sampling and measurement error variance.
NOTE: A single overall scale was used.
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2012 Reading Long-Term Trend Assessment.
9 1,041 194 0.53
13 1,266 210 0.51
17 1,265 203 0.44
Last updated 24 February 2016 (GF)
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