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, Science National Assessment, By Scale and Grade: 2011

NAEP Technical DocumentationProportion of scale score variance accounted for by the population-structure model, science 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
			Physical science	Earth and space sciences	Life science
1 (Total Variance – Residual Variance)/Total Variance, where Total Variance consists of both sampling and measurement error variance. 2 Excluding the constant term. NOTE: In 2011, only grade 8 was assessed. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2011 Science National Assessment.
8	2,668	837	0.62	0.59	0.58

Proportion of scale score variance accounted for by the population-structure model using a single overall scale, science 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. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2011 Science National Assessment.
8	2,668	837	0.59

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