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 U.S. History 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 12 U.S. history 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 U.S. History Assessment.
All contrasts	1025	0.90	0.61	1.00	14	62	380	309	260
Student questionnaire	208	0.89	0.61	0.99	6	24	64	71	43
Major reporting variables	61	0.91	0.74	1.00	0	5	23	12	21
Interactions between reporting variables	431	0.91	0.63	0.99	8	29	98	140	156
School questionnaire	290	0.89	0.82	0.99	0	0	180	76	34
SD/ELL questionnaire	35	0.89	0.78	0.96	0	4	15	10	6

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