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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 Models, Mathematics Long-Term Trend Assessment, by Age: 2004

NAEP Technical DocumentationProportion of scale score variance accounted for by the population-structure models, mathematics long-term trend assessment, by age: 2004

Age	Number of initial conditioning contrasts1	Number of principal components1	Proportion2 of scale score variance
9	1,504	130	0.35
13	1,761	157	0.43
17	1,768	156	0.42
1 Excluding the constant term. 2(Total Variance – Residual Variance)/Total Variance, where Total Variance consists of both sampling and measurement error variance. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2004 Mathematics Long-Term Trend Assessment.

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