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 Geography 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 geography 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 Geography Assessment.
All contrasts	1232	0.90	0.68	0.99	2	37	579	375	239
Student questionnaire	129	0.90	0.72	0.99	0	12	41	55	21
Major reporting variables	64	0.92	0.72	0.99	0	1	26	15	22
Interactions between reporting variables	352	0.91	0.68	0.98	2	22	100	114	114
Teacher questionnaire	394	0.89	0.81	0.99	0	0	243	102	49
School questionnaire	255	0.90	0.84	0.99	0	0	150	77	28
SD/ELL questionnaire	38	0.89	0.78	0.98	0	2	19	12	5

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