NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Item Blocks as Defined After Scaling, Age 17 Mathematics Long-Term Trend Assessment: 2008

NAEP Technical DocumentationOverall descriptive statistics for item blocks as defined after scaling, age 17 mathematics long-term trend assessment: 2008

Statistic	Item type	Block M1	Block M2	Block M3	Block M4	Block M5	Block M6
† 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 Mathematics Long-Term Trend Assessment.
Number of scaled items	Total	23	23	29	35	23	23
	Multiple choice	19	18	23	30	18	18
	Dichotomously scored constructed response	4	5	6	5	5	5
	Polytomously scored constructed response	0	0	0	0	0	0
Unweighted sample size	†	4,800	4,800	4,800	4,800	4,700	4,800
Weighted average item score	†	0.68	0.70	0.67	0.70	0.66	0.68
Weighted average polyserial	†	0.72	0.62	0.63	0.61	0.69	0.64
Weighted alpha reliability	†	0.89	0.81	0.87	0.89	0.87	0.84
Weighted proportion of students attempting last item1	†	0.92	0.97	0.81	0.72	0.93	0.98

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