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NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Item Blocks as Defined After Scaling, Grade 8 Vocabulary National Assessment, by Block and Item Type: 2015

NAEP Technical DocumentationOverall Descriptive Statistics for Item Blocks as Defined After Scaling, Grade 8 Vocabulary National Assessment, by Block and Item Type: 2015

Overall descriptive statistics for item blocks as defined after scaling, grade 8 vocabulary national assessment, by block and item type: 2015
Statistic	Item type	Block R14	Block R15	Block R16	Block R17	Block R18	Block R19	Embedded Items
Number of scaled items	Total	6	5	5	5	6	6	24
	Multiple choice	6	5	5	5	6	6	24
	Dichotomously scored constructed-response	†	†	†	†	†	†	†
	Polytomously scored constructed-response	†	†	†	†	†	†	†
Unweighted sample size¹	†	2,600	3,300	3,300	2,600	2,600	2,600	4,500
Weighted average item score²	†	.54	.57	.90	.78	.75	.66	.75
Weighted average polyserial	†	.67	.74	1.21	.92	.83	.76	.64
Weighted alpha reliability	†	.47	.49	.74	.62	.60	.59	†
Weighted proportion of students attempting last item³	†	.99	.99	1.00	.99	.99	.99	†
† Not applicable. ¹ The unweighted sample associated with the embedded items is the average unweighted sample across all embedded vocabulary items. ² The "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: The embedded items column contains information about all the vocabulary items embedded within the 25-minute reading comprehension blocks. 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 Reading Assessment.

Last updated 09 November 2021 (ML)

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