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 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 4 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	1252	0.90	0.69	0.99	1	41	579	390	241
Student questionnaire	137	0.90	0.71	0.99	0	11	33	71	22
Major reporting variables	64	0.92	0.74	0.99	0	1	24	16	23
Interactions between reporting variables	360	0.91	0.69	0.99	1	25	105	111	118
Teacher questionnaire	394	0.89	0.80	0.99	0	0	245	104	45
School questionnaire	258	0.90	0.83	0.99	0	0	154	74	30
SD/ELL questionnaire	39	0.88	0.79	0.98	0	4	18	14	3

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