NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Item Blocks as Defined After Scaling, by Block Designation, Grade 8 Reading Vocabulary National Assessment: 2009

NAEP Technical DocumentationOverall descriptive statistics for item blocks as defined after scaling, by block designation, grade 8 reading vocabulary national assessment: 2009

Statistic	Item type	Block R14	Block R15	Block R16	Block R17	Block R18	Block R19	Embedded blocks
† Not applicable. 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. The Embedded Blocks column contains information about all the Meaning 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 Meaning Vocabulary items SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2009 Reading Vocabulary Assessment.
Number of scaled items	Total	6	5	5	5	5	5	24
	Multiple choice	6	5	5	5	5	5	24
	Dichtomously scored constructed response	†	†	†	†	†	†	†
	Polytomously scored constructed response	†	†	†	†	†	†	†
Unweighted sample size	†	1,300	1,600	1,500	1,200	1,200	1,300	11,800
Weighted average item score	†	0.54	0.58	0.91	0.77	0.76	0.77	0.73
Weighted average polyserial	†	0.66	0.76	1.25	0.93	0.92	0.86	0.65
Weighted alpha reliability	†	0.44	0.53	0.75	0.62	0.67	0.49	†
Weighted proportion of students attempting last item1	†	1.00	1.00	1.00	0.99	0.99	1.00	†

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