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

NAEP Technical DocumentationOverall descriptive statistics for items as defined after scaling, grade 8 geography national assessment: 2010

Statistic	Item type	Block G3	Block G4	Block G5	Block G6	Block G7	Block G8	Block G9
† 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 Geography Assessment.
Number of scaled items	Total	17	16	16	16	15	17	25
	Multiple choice	12	11	11	12	11	12	15
	Dichtomously scored constructed response	0	1	1	0	0	0	3
	Polytomously scored constructed response	5	4	4	4	4	5	7
Unweighted sample size	†	2,500	2,400	2,400	2,400	2,400	2,400	2,200
Weighted average item score	†	.49	.51	.51	.41	.56	.48	.51
Weighted average polyserial	†	.56	.51	.54	.50	.60	.48	.51
Weighted alpha reliability	†	.73	.69	.74	.70	.74	.68	.78
Weighted proportion of students attempting last item	†	.98	.96	.93	.88	.80	.94	.99

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