NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Items as Defined After Scaling, Grade 4 Reading Vocabulary Combined National and State Assessments, By Block: 2011

NAEP Technical DocumentationOverall descriptive statistics for item blocks as defined after scaling, grade 4 reading vocabulary combined national and state assessments, by block: 2011

Statistic	Item type	Block R14	Block R15	Block R16	Block R17	Embedded blocks
† Not applicable. NOTE: The "weighted average item score" of polytomous items are standardized to have a scale of 0 to 1 so they are comparable to dichotomously scored items. The "weighted proportion of students attempting last item" is equal to 1 (percent not responding to last item /100). Item statistics in this table are described on the page Blocks of Items. The embedded blocks column contains information about all the reading vocabulary items embedded within the 25-minute reading comprehension blocks. The unweighted sample associated with the embedded items is the average unweighted sample across all embedded reading vocabulary items. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2011 Reading Vocabulary Assessment.
Number of scaled items	Total	5	5	5	5	20
	Multiple choice	5	5	5	5	20
	Dichtomously scored constructed response	†	†	†	†	†
	Polytomously scored constructed response	†	†	†	†	†
Unweighted sample size	†	9,500	9,500	9,500	9,400	40,500
Weighted average item score	†	.64	.56	.70	.52	.57
Weighted average polyserial	†	.83	.76	.91	.74	.58
Weighted alpha reliability	†	.64	.54	.72	.54	†
Weighted proportion of students attempting last item	†	.99	.99	.99	.97	†

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