NAEP Analysis and Scaling → Estimation of Population and Student Group Distributions → Examining the Population-Structure Models Used in NAEP → Proportion of Variance Accounted For by Principal Components Used in NAEP Population-Structure Models → Proportion of Variance of the Group-Defining Contrasts Accounted for by the Principal Components Used in the Population-Structure Model, Grade 12 Reading Vocabulary Combined National and State Main Assessment: 2009

NAEP Technical DocumentationProportion of variance of the group-defining contrasts accounted for by the principal components used in the population-structure model, grade 12 reading vocabulary combined national and state main assessment: 2009

Type of contrast	Number of contrasts	Mean	Minimum	Maximum	Number of contrasts by proportion1 of variance explained
					0.00 - 0.70	0.70 - 0.80	0.80 - 0.90	0.90 - 0.95	0.95 - 1.00
† Not applicable; Category does not exist. 1(Total Variance – Residual Variance)/Total Variance, where Total Variance consists of both sampling and measurement error variance. NOTE: NIES = National Indian Education Study; SD/ELL = Students with disabilities/English language learners. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2009 Reading Vocabulary Assessment.
All contrasts	98	0.90	0.65	1.00	6	7	22	27	36
Student questionnaire	5	0.98	0.96	1.00	0	0	0	0	5
Major reporting variables	29	0.93	0.85	1.00	0	0	10	10	9
Interaction between reporting variables	64	0.89	0.65	1.00	6	7	12	17	22
Teacher questionnaire	†	†	†	†	†	†	†	†	†
School questionnaire	†	†	†	†	†	†	†	†	†
NIES questionnaire	†	†	†	†	†	†	†	†	†
SD/ELL questionnaire	†	†	†	†	†	†	†	†	†

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