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 Main Assessment: 2009

NAEP Technical DocumentationOverall descriptive statistics for items as defined after scaling, grade 8 reading combined national and state main assessment: 2009

Statistic	Item type	Block F3	Block F4	Block F5	Block F6	Block F7	Block F8	Block F9	Block F10	Block F11	Block F12	Block F14	Block F15	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. 1 The "Weighted proportion of students attempting last item" is equal to 1 - (Percent not responding to last item /100). NOTE: 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), 2009 Reading Assessment.
Number of scaled items	Total	10	9	11	12	10	11	10	12	12	10	10	10	10	10	10	10	10	10	10	10	10	9	11	11	9
	Multiple choice	3	5	7	5	5	6	6	4	3	5	6	6	5	6	7	6	7	7	7	6	5	4	6	7	4
	Dichtomously scored constructed response	4	0	3	5	0	3	1	7	8	1	2	0	1	1	2	2	1	0	1	1	0	0	1	1	1
	Polytomously scored constructed response	3	4	1	2	5	2	3	1	1	4	2	4	4	3	1	2	2	3	2	3	5	5	4	3	4
Unweighted sample size	†	14,000	14,000	14,000	13,400	13,400	13,400	14,000	14,000	13,400	13,300	13,400	14,000	11,800	11,700	11,700	11,800	11,900	11,700	11,700	11,800	11,800	11,800	11,800	11,800	11,800
Weighted average item score	†	0.43	0.64	0.69	0.59	0.75	0.73	0.73	0.57	0.68	0.68	0.74	0.80	0.63	0.50	0.60	0.57	0.75	0.74	0.76	0.69	0.69	0.60	0.60	0.63	0.67
Weighted average polyserial	†	0.68	0.66	0.73	0.64	0.66	0.66	0.75	0.63	0.66	0.71	0.71	0.67	0.64	0.64	0.63	0.63	0.72	0.74	0.72	0.65	0.69	0.65	0.60	0.66	0.65
Weighted alpha reliability	†	0.75	0.67	0.77	0.71	0.65	0.67	0.74	0.74	0.75	0.76	0.69	0.65	0.72	0.70	0.67	0.66	0.72	0.73	0.67	0.64	0.73	0.70	0.71	0.73	0.67
Weighted proportion of students attempting last item1	†	0.83	0.92	0.95	0.90	0.97	0.95	0.99	0.79	0.87	0.96	0.87	0.96	0.85	0.92	0.96	0.98	0.96	0.97	0.94	0.95	0.95	0.97	0.75	0.88	0.93

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