NAEP Analysis and Scaling - Block-Level Descriptive Statistics as Defined After Scaling, Grade 8 Science Combined National and State Assessments, by Public and Nonpublic School Sessions: 2011

NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Block-Level Descriptive Statistics as Defined After Scaling, Grade 8 Science Combined National and State Assessments, by Public and Nonpublic School Sessions: 2011

NAEP Technical DocumentationBlock-level descriptive statistics as defined after scaling, grade 8 science combined national and state assessments, by public and nonpublic school sessions: 2011
Statistic	Type of school¹	Block S3	Block S4	Block S5	Block S6	Block S7	Block S8	Block S9	Block S11	Block S12
† Not applicable. ¹Nonpublic school sample includes only private and Catholic schools. 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. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2011 Science Assessment.
Number of scaled items	†	15	18	18	17	15	18	13	16	14
Unweighted sample size	Public	27,500	26,700	26,400	26,500	26,300	26,500	26,300	26,400	26,400
Unweighted sample size	Nonpublic	500	500	500	500	500	500	500	500	500
Weighted average item score	Public	.54	.49	.47	.48	.41	.47	.42	.41	.44
Weighted average item score	Nonpublic	.57	.54	.54	.54	.47	.53	.46	.44	.49
Weighted average polyserial	Public	.52	.52	.52	.51	.55	.54	.58	.54	.56
Weighted average polyserial	Nonpublic	.50	.51	.49	.52	.50	.55	.56	.54	.54
Weighted alpha reliability	Public	.73	.74	.75	.74	.74	.73	.72	.73	.72
Weighted alpha reliability	Nonpublic	.69	.70	.69	.75	.66	.73	.70	.73	.68
Weighted proportion of students attempting last item	Public	.88	.81	.87	.89	.76	.89	.94	.75	.83
Weighted proportion of students attempting last item	Nonpublic	.91	.90	.92	.93	.77	.87	.95	.77	.91

Last updated 05 January 2016 (GF)