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NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Item Blocks as Defined After Scaling, Grade 12 Science National Assessment, by Block and Item Type: 2015

NAEP Technical DocumentationOverall Descriptive Statistics for Item Blocks as Defined After Scaling, Grade 12 Science National Assessment, by Block and Item Type: 2015

Overall descriptive statistics for item blocks as defined after scaling, grade 12 science national 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	Block S13
Number of scaled items	Total	16	17	17	17	16	17	19	17	16	15	14
	Multiple choice	10	12	12	12	10	11	16	13	11	10	9
	Dichotomously scored constructed-response	1	0	2	1	1	0	0	1	0	0	0
	Polytomously scored constructed-response	5	5	3	4	5	6	3	3	5	5	5
Unweighted sample size	†	2,000	2,000	2,000	2,000	2,000	2,000	2,000	2,000	2,000	2,000	2,000
Weighted average item score¹	†	.48	.43	.41	.40	.44	.44	.52	.51	.44	.40	.41
Weighted average polyserial	†	.60	.56	.50	.56	.59	.59	.58	.56	.57	.54	.56
Weighted alpha reliability	†	.78	.75	.69	.75	.77	.80	.79	.76	.72	.67	.72
Weighted proportion of students attempting last item²	†	.89	.91	.89	.89	.94	.94	.92	.93	.95	.96	.90
† 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 dichotomouly 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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