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

Overall descriptive statistics for item blocks as defined after scaling, grade 8 reading combined national and state assessment, by block and item type: 2015
Statistic	Item type	Block R1	Block R2	Block R3	Block R4	Block R5	Block R6	Block R7	Block R8	Block R9	Block R10	Block R11	Block R12	Block R13
Number of scaled items	Total	10	10	10	10	10	10	10	10	10	10	11	10	10
	Multiple choice	5	6	7	6	6	7	7	6	5	5	7	5	6
	Dichotomously scored constructed-response	1	0	2	1	1	0	1	1	0	0	0	2	1
	Polytomously scored constructed-response	4	4	1	3	3	3	2	3	5	5	4	3	3
Unweighted sample size	†	21,000	20,800	21,000	21,000	21,100	20,900	21,000	21,000	20,900	21,000	20,900	20,900	21,000
Weighted average item score¹	†	.65	.66	.61	.49	.78	.74	.76	.75	.68	.63	.69	.65	.64
Weighted average polyserial	†	.64	.65	.63	.63	.75	.74	.73	.78	.67	.66	.67	.66	.69
Weighted alpha reliability	†	.72	.73	.67	.71	.72	.73	.68	.75	.72	.72	.76	.73	.72
Weighted proportion of students attempting last item²	†	.82	.90	.94	.72	.97	.95	.93	.95	.93	.92	.91	.77	.92
† Not applicable. ¹ 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. 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), 2015 Reading Assessment.

Last updated 09 November 2021 (ML)