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, Writing Combined National and State Main Assessment, By Scale and Grade: 2011

NAEP Technical DocumentationProportion of scale score variance accounted for by the population-structure model, writing national assessment, by scale and grade: 2011

Grade	Number of initial conditioning contrasts2	Number of principal components2	Proportion1 of scale score variance by the population-structure model
			One Scale3
1 (Total Variance – Residual Variance)/Total Variance, where Total Variance consists of both sampling and measurement error variance. 2 Excluding the constant term. 3 Single overall scale. NOTE: At grade 12, the Measurement and Geometry subscales were combined for scaling. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2011 Writing National Assessment.
8	2,134	594	1.00
12	1,821	461	1.00

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