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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 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 8 Writing National Assessment: 2011

NAEP Technical DocumentationProportion of variance of the group-defining contrasts accounted for by the principal components used in the population-structure model, grade 8 writing national assessment: 2011
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.
NOTE: NIES = National Indian Education Study; SD/ELL = Students with disabilities/English language learners.
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2011 Writing Assessment.
All contrasts 1297 0.90 0.62 1.00 11 46 533 454 253
Student questionnaire 392 0.91 0.62 0.99 2 11 124 163 92
Major reporting variables 64 0.92 0.80 1.00 0 0 26 12 26
Interactions between reporting variables 322 0.89 0.67 0.98 9 22 103 139 49
Teacher questionnaire 324 0.89 0.73 0.98 0 8 173 95 48
School questionnaire 159 0.89 0.79 0.99 0 2 97 39 21
SD/ELL questionnaire 36 0.91 0.74 0.98 0 3 10 6 17
Last updated 05 January 2016 (GF)
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