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, Reading Vocabulary Combined National and State Assessments, By Scale and Grade: 2011

NAEP Technical DocumentationProportion of scale score variance accounted for by the population-structure models, reading vocabulary combined national and state assessments, by scale and grade: 2011

Grade	Number of initial conditioning contrasts2	Number of principal components2	Proportion1 of scale score variance
			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: In 2011,  grade 12 reading vocabulary was not assessed. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2011 Reading Vocabulary Assessment.
4	1189	151	0.34
8	1194	145	0.36

Printer-friendly Version