NAEP Technical DocumentationProportion of Variance of the Group-Defining Contrasts Accounted for by the Principal Components Used in the Population-Structure Model, Grade 8 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 8 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	1653	.90	.66	1.00	11	56	757	567	262
Student questionnaire	68	.88	.67	.98	2	14	16	19	17
Major reporting variables	223	.91	.70	1.00	1	8	80	79	55
Interactions between reporting variables	350	.89	.66	.98	8	21	121	158	42
Teacher questionnaire	287	.90	.76	.99	0	6	144	90	47
School questionnaire	693	.90	.81	.99	0	0	387	214	92
SD/EL questionnaire	32	.88	.77	.98	0	7	9	7	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.

Printer-friendly Version