NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Block-Level Descriptive Statistics as Defined After Scaling, Grade 8 Writing National Assessment, by Public and Nonpublic School Sessions: 2011

NAEP Technical DocumentationBlock-level descriptive statistics as defined after scaling, grade 8 writing national assessment, by public and nonpublic school sessions: 2011

Statistic	Type of school1	Block W
† Not applicable. 1 Nonpublic school sample includes only private and Catholic schools. NOTE: The "weighted average item score" of polytomous items are standardized to have a scale of 0 to 1 so they are comparable to dichotomously scored items. The "weighted proportion of students attempting last item" is equal to 1- (percent not responding to last item /100). Item statistics in this table are described on the page Blocks of Items. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2011 Writing Assessment.
Number of scaled items	†	22
Unweighted sample size	Public	22,100
	Nonpublic	2,100
Weighted average item score	Public	.48
	Nonpublic	.56
Weighted average polyserial	Public	.68
	Nonpublic	.92
Weighted alpha reliability	Public	†
	Nonpublic	†
Weighted proportion of students attempting last item	Public	†
	Nonpublic	†

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