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NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Item Blocks as Defined After Scaling, Grade 4 Science National Main Assessment (Accommodations Not Permitted [R2]): 2000

NAEP Technical DocumentationOverall descriptive statistics for item blocks as defined after scaling, grade 4 science national main assessment (accommodations not permitted [R2]): 2000

Statistic	Item type	Block S3	Block S4	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	Total	6	7	4	10	15	8	11	14	11	11	10	9	14	11
	Multiple choice	0	1	0	2	13	1	6	10	6	6	5	3	10	5
	Dichotomously scored constructed response	1	5	1	4	2	2	1	1	0	2	1	0	0	1
	Polytomously scored constructed response	5	1	3	4	0	5	4	3	5	3	4	6	4	5
Unweighted sample size		2,500	2,500	2,200	3,400	3,300	3,500	2,600	2,500	2,500	2,500	3,400	2,500	2,500	2,600
Weighted average item score		0.37	0.47	0.51	0.46	0.48	0.36	0.45	0.49	0.49	0.53	0.32	0.31	0.49	0.46
Weighted average polyserial		0.65	0.70	0.77	0.59	0.53	0.64	0.61	0.51	0.61	0.54	0.55	0.62	0.50	0.61
Weighted alpha reliability		0.54	0.52	0.64	0.68	0.63	0.58	0.70	0.63	0.69	0.59	0.52	0.56	0.62	0.66
Weighted proportion of students attempting last item1		77.06	83.41	68.35	86.19	86.58	82.15	88.10	81.87	66.54	91.25	84.96	82.87	77.95	64.78
1 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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