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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, Geography National Main Assessment (Accommodations Not Permitted ): 2001

NAEP Technical DocumentationProportion of scale score variance accounted for by the population-structure model and grade, geography national main assessment (accommodations not permitted [R2]): 2001

Grade	Number of initial group-defining contrasts2	Number of principal components2	Proportion1 of scale score variance
			Space and place	Environment and society	Spatial dynamics and connections
4	870	298	0.60	0.65	0.65
8	1,051	364	0.63	0.62	0.65
12	762	273	0.58	0.58	0.58
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), 2001 Geography Assessment.

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