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NAEP Analysis and Scaling → Estimation of Population and Student Group Distributions → Examining the Population-Structure Models Used in NAEP → Proportion of Variance of the Group-Defining Contrasts Accounted for by the Principal Components Used in NAEP Student Group Distribution Models → Proportion of Variance of the Group-Defining Contrasts Accounted for by the Principal Components Used in the Population-Structure Model, Grade 12 Science National Main Assessment: 2005

NAEP Technical DocumentationProportion of variance of the group-defining contrasts accounted for by the principal components used in the population-structure model, grade 12 science national main assessment: 2005

Type of contrast	Number of contrasts	Mean	Minimum	Maximum	Number of contrasts by proportion1 of variance explained
					0.00 - 0.70	0.71 - 0.80	0.81 - 0.90	0.91 - 0.95	0.96 - 1.00
1(Total Variance – Residual Variance)/Total Variance, where Total Variance consists of both sampling and measurement error variance. NOTE: Teacher questionnaire was not included at grade 12 in 2005. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2005 Science Assessment.
All contrasts	1,005	0.90	0.62	0.99	15	56	376	286	272
Student questionnaire	246	0.89	0.67	0.99	2	17	110	86	31
Major reporting variables	58	0.92	0.79	0.99	0	2	22	5	29
Interactions between reporting variables	532	0.91	0.62	0.99	13	25	136	147	211
School questionnaire	169	0.87	0.75	0.95	0	12	108	48	1

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