NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Items as Defined After Scaling, Grade 4 Reading Combined National and State Assessments, By Block: 2011

NAEP Technical DocumentationOverall descriptive statistics for items as defined after scaling, grade 4 reading combined national and state assessments, by block: 2011

Statistic	Item type	Block R1	Block R2	Block R3	Block R4	Block R5	Block R6	Block R7	Block R8	Block R9	Block R10
† 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), 2011 Reading Assessment.
Number of scaled items	Total	11	8	11	10	10	10	10	10	9	10
	Multiple choice	6	5	7	6	7	7	7	6	6	6
	Dichtomously scored constructed response	1	1	0	1	1	0	0	1	1	0
	Polytomously scored constructed response	4	2	4	3	2	3	3	3	2	4
Unweighted sample size	†	40,700	40,600	40,500	40,400	40,400	40,500	40,500	40,600	40,500	40,500
Weighted average item score	†	.62	.64	.63	.62	.49	.51	.57	.51	.59	.50
Weighted average polyserial	†	.64	.68	.62	.62	.62	.65	.62	.63	.69	.60
Weighted alpha reliability	†	.74	.67	.71	.74	.71	.74	.71	.70	.72	.71
Weighted proportion of students attempting last item	†	.82	.81	.79	.78	.76	.78	.78	.75	.86	.71

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