NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Block-Level Descriptive Statistics as Defined After Scaling, Grade 8 Geography National Assessment, by Public and Nonpublic School Sessions: 2010

NAEP Technical DocumentationBlock-level descriptive statistics as defined after scaling, grade 8 geography national assessment, by public and nonpublic school sessions: 2010

Statistic	Type of school1	Block G3	Block G4	Block G5	Block G6	Block G7	Block G8	Block G9
† 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 Geography Assessment.
Number of scaled items	†	17	16	16	16	15	17	25
Unweighted sample size	Public	2,300	2,200	2,200	2,200	2,200	2,200	2,000
	Nonpublic	190	190	180	190	190	190	190
Weighted average item score	Public	.48	.50	.50	.40	.55	.47	.50
	Nonpublic	.57	.59	.60	.47	.66	.54	.57
Weighted average polyserial	Public	.55	.50	.53	.50	.60	.48	.51
	Nonpublic	.55	.47	.55	.51	.57	.50	.48
Weighted alpha reliability	Public	.73	.69	.73	.69	.74	.67	.78
	Nonpublic	.73	.62	.72	.70	.71	.68	.74
Weighted proportion of students attempting last item	Public	.98	.96	.93	88	.80	.94	.99
	Nonpublic	.99	.98	.96	.90	.84	.96	1.00

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