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

NAEP Technical DocumentationBlock-Level Descriptive Statistics as Defined After Scaling, Grade 8 Mathematics Combined National and State Assessment, by Block and School Type: 2015

Block-level descriptive statistics as defined after scaling, grade 8 mathematics combined national and state assessment, by block and school type: 2015
Statistic	Type of school¹	Block M3	Block M4	Block M5	Block M6	Block M7	Block M8	Block M9	Block M10	Block M11	Block M12
Number of scaled items	†	14	14	15	15	15	15	15	15	17	15
Unweighted sample size	Public	25,600	25,400	25,600	25,600	28,700	28,500	28,500	25,700	25,600	25,700
Unweighted sample size	Nonpublic	400	400	500	400	500	400	400	500	500	400
Weighted average item score²	Public	.52	.44	.46	.47	.43	.52	.58	.54	.46	.54
Weighted average item score²	Nonpublic	.60	.47	.52	.54	.49	.60	.66	.61	.51	.59
Weighted average polyserial	Public	.61	.67	.54	.65	.63	.70	.69	.62	.59	.63
Weighted average polyserial	Nonpublic	.61	.67	.55	.63	.60	.67	.69	.63	.57	.59
Weighted alpha reliability	Public	.75	.80	.72	.81	.77	.84	.82	.77	.79	.75
Weighted alpha reliability	Nonpublic	.74	.80	.71	.78	.73	.81	.81	.76	.77	.70
Weighted proportion of students attempting last item³	Public	.86	.91	.78	.90	.90	.96	.93	.87	.82	.81
Weighted proportion of students attempting last item³	Nonpublic	.93	.97	.87	.96	.96	.98	.98	.93	.93	.84
† 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. ²The "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 Mathematics Assessment.

Last updated 09 November 2021 (ML)

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