NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Items as Defined After Scaling, Grade 8 Reading Combined National and State Assessments, By Block: 2011

NAEP Technical DocumentationOverall descriptive statistics for items as defined after scaling, grade 8 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	Block R11	Block R12	Block R13
† 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	10	10	10	10	10	10	10	10	10	10	11	10	9
	Multiple choice	5	6	7	6	7	7	7	6	5	5	6	5	4
	Dichtomously scored constructed response	1	1	2	2	1	0	1	1	0	0	1	2	1
	Polytomously scored constructed response	4	3	1	2	2	3	2	3	5	5	4	3	4
Unweighted sample size	†	24,900	24,900	24,800	24,800	24,800	24,800	24,900	24,900	24,900	24,800	24,800	24,700	24,900
Weighted average item score	†	.65	.49	.60	.56	.75	.74	.76	.70	.69	.62	.62	.65	.68
Weighted average polyserial	†	.63	.63	.62	.63	.71	.74	.72	.63	.69	.65	.60	.66	.63
Weighted alpha reliability	†	.71	.70	.65	.67	.72	.73	.66	.62	.73	.71	.70	.72	.64
Weighted proportion of students attempting last item	†	.84	.91	.96	.97	.96	.97	.94	.94	.95	.94	.73	.81	.94

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