NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Block-Level Descriptive Statistics as Defined After Scaling, Grade 12 Civics National Assessment, by Public and Nonpublic School Sessions: 2010

NAEP Technical DocumentationBlock-level descriptive statistics as defined after scaling, grade 12 civics national assessment, by public and nonpublic school sessions: 2010

Statistic	Type of school1	Block C3	Block C4	Block C5	Block C6	Block C7	Block C8	Block C9	Block C10
† 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), 2010 Civics Assessment.
Number of scaled items	†	19	19	20	18	19	19	19	19
Unweighted sample size	Public	2,200	2,200	2,200	2,300	2,100	2,200	2,200	2,200
	Nonpublic	300	270	280	270	290	280	290	290
Weighted average item score	Public	.49	.54	.54	.54	.48	.49	.57	.55
	Nonpublic	.54	.60	.60	.61	.55	.59	.62	.60
Weighted average polyserial	Public	.60	.54	.55	.54	.51	.57	.58	.55
	Nonpublic	.62	.54	.53	.55	.52	.58	.61	.58
Weighted alpha reliability	Public	.82	.74	.79	.73	.74	.79	.80	.76
	Nonpublic	.84	.73	.75	.73	.75	.78	.81	.77
Weighted proportion of students attempting last item	Public	.92	.97	.92	.96	.91	.92	.96	.95
	Nonpublic	.93	.98	.97	.95	.93	.93	.98	.99

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