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NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Item-Level Descriptive Statistics as Defined After Scaling, Grade 8 Writing Combined National and State Main Assessment, by Public and Nonpublic School Sessions: 2007

NAEP Technical DocumentationItem-level descriptive statistics as defined after scaling, grade 8 writing combined national and state main assessment, by public and nonpublic school sessions: 2007

Statistic	Type of school	All items
† Not applicable. 1 The "Weighted proportion of students attempting last item" is equal to 1 - (Percent not responding to last item /100). NOTE: Nonpublic-school samples include only Catholic and private schools. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2007 Writing Assessment.
Number of scaled items	†	20
Unweighted sample size	Public	135,100
	Nonpublic	3,100
Weighted average item score	Public	0.55
	Nonpublic	0.63
Weighted average polyserial	Public	0.91
	Nonpublic	0.90
Weighted alpha reliability	Public	†
	Nonpublic	†
Weighted proportion of students attempting last item1	Public	†
	Nonpublic	†

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