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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 Model and Grade, Science National Main Assessment (Accommodations Permitted): 2000

NAEP Technical DocumentationProportion of scale score variance accounted for by the population-structure model and grade, science national main assessment (accommodations permitted [R3]): 2000

Grade	Number of initial group-defining contrasts2	Number of principal components2	Proportion1 of scale score variance
			Physical science	Earth science	Life science
4	970	373	0.61	0.60	0.58
8	1,081	420	0.67	0.63	0.65
12	1,173	395	0.68	0.66	0.68
1 Proportion is (Total Variance – Residual Variance)/Total Variance. 2 Excluding the constant term.
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2000 Science Assessment.

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