NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Items as Defined After Scaling, Grade 8 U.S. History National Assessment: 2010

NAEP Technical DocumentationOverall descriptive statistics for items as defined after scaling, grade 8 U.S. history national assessment: 2010

Statistic	Item type	Block H3	Block H4	Block H5	Block H6	Block H7	Block H8	Block H9	Block H10	Block H11	Block H12
† Not applicable. 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 U.S. History Assessment.
Number of scaled items	Total	17	16	17	16	16	17	17	16	16	16
	Multiple choice	12	11	12	11	12	13	12	11	11	11
	Dichtomously scored constructed response	2	0	0	1	0	0	0	1	0	0
	Polytomously scored constructed response	3	5	5	4	4	4	5	4	5	5
Unweighted sample size	†	2,400	2,400	2,300	2,300	2,300	2,400	2,400	2,400	2,400	2,400
Weighted average item score	†	.58	.47	.45	.48	.51	.50	.40	.40	.39	.48
Weighted average polyserial	†	.57	.53	.57	.53	.55	.53	.51	.49	.50	.56
Weighted alpha reliability	†	.74	.75	.74	.73	.75	.75	.71	.62	.67	.77
Weighted proportion of students attempting last item	†	.96	.96	.91	.95	.97	.90	.94	.92	.95	.94

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