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, Civics National Assessment, By Scale and Grade: 2010

NAEP Technical DocumentationProportion of scale score variance accounted for by the population-structure model, civics national assessment, by scale and grade: 2010

Grade	Number of initial conditioning contrasts1	Number of principal components1	Proportion2 of scale score variance
			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 for civics. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2010 Civics Assessment.
			4	2699	450	0.64
8	3079	488	0.69
12	2735	364	0.68

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