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NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Block-Level Descriptive Statistics by Public- and Nonpublic-School Sessions, as Defined After Scaling, Grade 8 Science National Main Assessment (Accommodations Not Permitted [R2]): 2000

NAEP Technical DocumentationBlock-level descriptive statistics by public- and nonpublic-school sessions, as defined after scaling, grade 8 science national main assessment (accommodations not permitted [R2]): 2000

Statistic	Type of school1	Block S3	Block S5	Block S6	Block S7	Block S8	Block S9	Block S10	Block S11	Block S12	Block S13	Block S14	Block S15	Block S20	Block S21
Number of Scaled Items	†	6	8	6	20	10	13	20	16	16	15	16	15	20	16
Unweighted sample size	Public	1,500	1,500	1,500	2,000	2,100	2,000	1,500	1,500	1,600	1,500	2,000	1,500	1,500	1,500
	Nonpublic	1,000	1,000	1,000	1,400	1,300	1,500	1,000	1,000	1,000	1,000	1,300	1,100	1,100	1,100
Weighted average item score	Public	0.48	0.38	0.28	0.43	0.56	0.51	0.48	0.45	0.33	0.40	0.46	0.35	0.42	0.42
	Nonpublic	0.55	0.46	0.33	0.50	0.63	0.56	0.56	0.52	0.40	0.45	0.52	0.41	0.47	0.49
Weighted alpha reliability	Public	0.75	0.71	0.39	0.71	0.67	0.68	0.76	0.73	0.72	0.68	0.72	0.70	0.70	0.73
	Nonpublic	0.65	0.70	0.40	0.69	0.56	0.63	0.73	0.69	0.68	0.60	0.69	0.65	0.68	0.65
Weighted average polyserial	Public	0.75	0.76	0.75	0.50	0.69	0.58	0.54	0.55	0.56	0.52	0.56	0.56	0.49	0.53
	Nonpublic	0.70	0.73	0.71	0.49	0.65	0.56	0.52	0.53	0.52	0.48	0.53	0.51	0.48	0.49
Weighted proportion of students attempting last item2	Public	0.72	0.47	0.79	0.81	0.96	0.93	0.97	0.77	0.79	0.91	0.97	0.85	0.98	0.87
	Nonpublic	0.84	0.53	0.85	0.89	0.98	0.98	0.99	0.90	0.88	0.97	0.96	0.91	0.99	0.93
† Not applicable. 1 Nonpublic-school sample includes only Catholic and private schools. 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), 2000 Science Assessment.

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