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

NAEP Technical DocumentationOverall descriptive statistics for item blocks as defined after scaling, age 13 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	27	37	23	23
	Multiple choice	18	18	19	29	18	18
	Dichotomously scored constructed response	5	5	8	8	5	5
	Polytomously scored constructed response	0	0	0	0	0	0
Unweighted sample size	†	4,300	4,200	4,300	4,200	4,200	4,200
Weighted average item score	†	0.70	0.71	0.67	0.69	0.62	0.69
Weighted average polyserial	†	0.62	0.59	0.62	0.56	0.59	0.61
Weighted alpha reliability	†	0.83	0.80	0.88	0.87	0.82	0.82
Weighted proportion of students attempting last item1	†	0.98	0.95	0.85	0.74	0.94	0.97

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