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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 Model → Proportion of Scale Score Variance Accounted for by the Population-Structure Models, Reading Long-Term Trend Assessment, By Age: 2008

NAEP Technical DocumentationProportion of scale score variance accounted for by the population-structure models, reading long-term trend assessment, by age: 2008
1 Excluding the constant term.
2(Total Variance – Residual Variance)/Total Variance, where Total Variance consists of both sampling and measurement error variance.
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2008 Reading Long-Term Trend Assessment.
Age Number of initial group-defining contrasts1 Number of principal components1 Proportion2 of scale score variance
9 1,844 177 0.48
13 2,164 199 0.47
17 2,167 186 0.45
Last updated 14 December 2011 (GF)
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