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 8 Reading Combined National and State Assessments: 2011

NAEP Technical DocumentationProportion of variance of the group-defining contrasts accounted for by the principal components used in the population-structure model, grade 8 reading combined national and state assessments: 2011

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
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), 2011 Reading Assessment.
All contrasts	2046	0.90	0.65	1.00	12	84	850	674	426
Student questionnaire	63	0.90	0.70	0.99	1	9	11	20	22
Major reporting variables	248	0.92	0.66	1.00	3	11	59	97	78
Interactions between reporting variables	372	0.90	0.65	0.98	7	25	99	173	68
Teacher questionnaire	301	0.92	0.75	0.99	0	6	88	84	123
School questionnaire	702	0.90	0.77	0.99	0	7	391	224	80
NIES questionnaire	323	0.87	0.70	0.99	1	25	191	69	37
SD/ELL questionnaire	37	0.92	0.80	1.00	0	1	11	7	18

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