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

NAEP Technical DocumentationBlock-Level Descriptive Statistics as Defined After Scaling, Grade 12 Science National Assessment, by Block and School Type: 2015

Block-level descriptive statistics as defined after scaling, grade 12 science national assessment, by block and school type: 2015
Statistic	Type of school¹	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	†	16	17	17	17	16	17	19	17	16	15	14
Unweighted sample size	Public	1,800	1,900	1,800	1,800	1,900	1,800	1,800	1,900	1,800	1,800	1,800
Unweighted sample size	Nonpublic	200	200	200	200	200	200	200	200	200	200	200
Weighted average item score²	Public	.47	.43	.40	.39	.44	.44	.51	.51	.44	.40	.41
Weighted average item score²	Nonpublic	.55	.50	.47	.46	.50	.50	.60	.58	.48	.43	.46
Weighted average polyserial	Public	.60	.56	.50	.57	.59	.59	.58	.56	.57	.54	.56
Weighted average polyserial	Nonpublic	.63	.54	.50	.52	.55	.57	.58	.57	.52	.58	.56
Weighted alpha reliability	Public	.77	.75	.69	.75	.78	.80	.79	.76	.73	.66	.72
Weighted alpha reliability	Nonpublic	.79	.74	.68	.73	.72	.78	.78	.76	.65	.72	.70
Weighted proportion of students attempting last item³	Public	.89	.91	.88	.89	.94	.94	.92	.93	.95	.95	.90
Weighted proportion of students attempting last item³	Nonpublic	.92	.92	.94	.90	.95	.99	.93	.94	.98	.97	.90
† Not applicable. ¹ Nonpublic school sample includes only private schools, including Catholic schools. BIE and DoDEA schools are not included in either the public or nonpublic category. ² 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. ³ 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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