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 4 Civics National Assessment: 2010

NAEP Technical DocumentationProportion of variance of the group-defining contrasts accounted for by the principal components used in the population-structure model, grade 4 civics national assessment: 2010

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. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2010 Civics Assessment.
All contrasts	1304	0.90	0.68	0.99	3	35	630	381	255
Student questionnaire	157	0.89	0.69	0.99	1	13	68	55	20
Major reporting variables	66	0.92	0.72	0.99	0	1	29	13	23
Interactions between reporting variables	393	0.91	0.68	0.99	2	21	113	124	133
Teacher questionnaire	396	0.89	0.80	0.99	0	0	250	96	50
School questionnaire	254	0.90	0.85	0.99	0	0	147	82	25
SD/ELL questionnaire	38	0.89	0.80	0.98	0	0	23	11	4

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