NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Item Blocks as Defined After Scaling, Age 13 Reading Long-Term Trend Assessment: 2008

NAEP Technical DocumentationOverall descriptive statistics for item blocks as defined after scaling, age 13 reading long-term trend assessment: 2008

Statistic	Item type	Block R21	Block R22	Block R23	Block R24	Block R25	Block R26	Block R27	Block R28	Block R29	Block R30
† 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), 2008 Reading Long-Term Trend Assessment.
Number of scaled items	Total	10	9	11	11	10	13	11	10	10	10
	Multiple choice	9	8	10	10	9	13	11	9	9	10
	Dichotomously scored constructed response	0	0	0	0	0	0	0	0	0	0
	Polytomously scored constructed response	1	1	1	1	1	0	0	1	1	0
Unweighted sample size	†	2,500	2,600	2,500	2,500	2,500	2,600	2,500	2,500	2,500	2,500
Weighted average item score	†	0.70	0.76	0.79	0.69	0.68	0.81	0.76	0.71	0.76	0.77
Weighted average polyserial	†	0.70	0.72	0.72	0.64	0.75	0.75	0.69	0.67	0.75	0.73
Weighted alpha reliability	†	0.69	0.64	0.67	0.70	0.78	0.77	0.67	0.71	0.67	0.70
Weighted proportion of students attempting last item1	†	0.91	0.96	0.94	0.90	0.94	0.95	0.96	0.88	0.92	0.96

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