NAEP Technical Documentation Proportion of Variance of the Group-Defining Contrasts Accounted for by the Principal Components Used in the Population-Structure Model, Grade 4  Vocabulary National Assessment, by Type of Contrast: 2015

Proportion of variance of the group-defining contrasts accounted for by the principal components used in the population-structure model, grade 4 vocabulary national assessment, by type of contrast: 2015

Type of contrast	Number of contrasts	Mean	Minimum	Maximum	Number of contrasts by proportion of variance explained1
					.00 - .70	.70 - .80	.80 - .90	.90 - .95	.95 - 1.00
All contrasts	2030	.90	.67	1.00	4	31	1044	619	332
Student questionnaire	53	.89	.72	.98	0	9	12	17	15
Major reporting variables	168	.91	.71	1.00	0	5	70	54	39
Interactions between reporting variables	258	.89	.67	.97	4	15	103	109	27
Teacher questionnaire	853	.90	.80	.99	0	0	489	208	156
School questionnaire	664	.90	.80	.99	0	0	356	222	86
SD/EL questionnaire	34	.90	.78	.98	0	2	14	9	9
1 (Total Variance – Residual Variance) / Total Variance, where Total Variance consists of sampling, measurement, and other sources of error. NOTE: SD/EL = Students with disabilities/English learners. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2015 Reading Assessment.

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