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

NAEP Technical DocumentationBlock-level descriptive statistics as defined after scaling, grade 8 reading combined national and state assessments, by public and nonpublic school sessions: 2011

Statistic	Type of school1	Block R1	Block R2	Block R3	Block R4	Block R5	Block R6	Block R7	Block R8	Block R9	Block R10	Block R11	Block R12	Block R13
† 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 Reading Assessment
Number of scaled items	†	10	10	10	10	10	10	10	10	10	10	11	10	9
Unweighted sample size	Public	23,400	23,300	23,200	23,300	23,300	23,300	23,400	23,300	23,400	23,300	23,300	23,200	23,400
	Nonpublic	1,200	1,200	1,200	1,200	1,200	1,200	1,200	1,200	1,200	1,200	1,200	1,200	1,200
Weighted average item score	Public	.64	.48	.60	.55	.74	.74	.76	.70	.68	.62	.61	.65	.67
	Nonpublic	.73	.58	.70	.65	.83	.81	.83	.76	.76	.70	.70	.72	.75
Weighted average polyserial	Public	.63	.63	.62	.63	.71	.74	.71	.64	.68	.65	.60	.66	.64
	Nonpublic	.60	.62	.61	.61	.69	.77	.71	.55	.65	.61	.58	.63	.57
Weighted alpha reliability	Public	.71	.70	.65	.67	.72	.73	.66	.63	.73	.71	.70	.72	.65
	Nonpublic	.62	.65	.59	.60	.63	.69	.54	.48	.63	.63	.64	.62	.53
Weighted proportion of students attempting last item	Public	.84	.91	.96	.97	.96	.97	.94	.94	.95	.94	.73	.80	.93
	Nonpublic	.93	.95	.98	.98	.98	.98	.97	.97	.97	.97	.79	.90	.97

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