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NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Item Blocks as Defined After Scaling, Grade 8 Mathematics Combined National and State Assessment, by Block and Item Type: 2015

NAEP Technical DocumentationOverall Descriptive Statistics for Item Blocks as Defined After Scaling, Grade 8 Mathematics Combined National and State Assessment, by Block and Item Type: 2015

Overall descriptive statistics for item blocks as defined after scaling, grade 8 mathematics combined national and state assessment, by block and item type: 2015
Statistic	Item type	Block M3	Block M4	Block M5	Block M6	Block M7	Block M8	Block M9	Block M10	Block M11	Block M12
Number of scaled items	Total	14	14	15	15	15	15	15	15	17	15
	Multiple choice	9	11	11	11	10	12	12	11	12	11
	Dichotomously scored constructed-response	0	0	1	1	3	0	1	0	0	3
	Polytomously scored constructed-response	5	3	3	3	2	3	2	4	5	1
Unweighted sample size	†	26,500	26,300	26,500	26,400	29,600	29,300	29,400	26,600	26,500	26,500
Weighted average item score¹	†	.52	.45	.46	.47	.44	.53	.59	.55	.46	.55
Weighted average polyserial	†	.62	.67	.54	.65	.63	.70	.69	.62	.59	.62
Weighted alpha reliability	†	.75	.80	.72	.81	.77	.84	.82	.77	.79	.74
Weighted proportion of students attempting last item²	†	.86	.92	.79	.90	.90	.96	.93	.88	.83	.81
† Not applicable. ¹ The "Weighted average item score" of polytomous items is standardized to have a scale of 0 to 1 so they are comparable to dichotomously scored items. ² 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), 2015 Mathematics Assessment.

Last updated 05 November 2021 (ML)

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