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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 Science 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 Science Combined National and State Assessment, by Block and Item Type: 2015

Overall descriptive statistics for item blocks as defined after scaling, grade 8 science combined national and state assessment, by block and item type: 2015
Statistic	Item type	Block S3	Block S4	Block S5	Block S6	Block S7	Block S8	Block S9	Block S10	Block S11	Block S12
Number of scaled items	Total	15	18	18	17	15	17	13	17	16	15
	Multiple choice	10	13	13	11	9	12	7	14	12	9
	Dichotomously scored constructed-response	0	0	0	0	0	1	0	1	0	1
	Polytomously scored constructed-response	5	5	5	6	6	4	6	2	4	5
Unweighted sample size	†	22,000	22,000	22,000	22,000	22,000	22,000	22,000	22,000	22,000	22,000
Weighted average item score¹	†	.56	.50	.48	.50	.43	.50	.43	.60	.58	.45
Weighted average polyserial	†	.52	.53	.52	.52	.55	.53	.58	.56	.58	.56
Weighted alpha reliability	†	.73	.75	.75	.76	.74	.72	.72	.75	.75	.74
Weighted proportion of students attempting last item²	†	.85	.77	.84	.86	.71	.87	.91	.93	.91	.79
† 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 Science Assessment.

Last updated 09 November 2021 (ML)

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