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NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Block-Level Descriptive Statistics as Defined After Scaling, Grade 4 Science National Assessment, by Block and School Type: 2019

NAEP Technical DocumentationBlock-Level Descriptive Statistics as Defined After Scaling, Grade 4 Science National Assessment, by Block and School Type: 2019

Block-level descriptive statistics as defined after univariate scaling, grade 4 science DBA national assessment, by block and school type: 2019
Statistic	Block S2	Block S3	Block S4	Block S5	Block S6	Block S7	Block S8	Block S9	Block S10	Block S11	Block H2	Block I1	Block I3
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.
The "Weighted proportion of students attempting last item" is equal to 1 – (Percent not responding to last item / 100). Weights are applied to reflect sampling design.
DBA = Digitally based assessment. The nonpublic school sample includes only private schools, including Catholic schools. BIE and DoDEA schools are not included in either the public or nonpublic category. Item statistics in this table are described on the page Blocks of Items.
U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2019 Science Assessment.
Number of scaled items	16	17	16	16	16	17	15	17	16	17	5	10	7
Public school
Unweighted sample size	2,900	3,100	3,000	3,000	2,900	3,000	3,100	3,000	2,900	3,000	2,300	2,500	2,600
Weighted average item score	.53	.43	.54	.40	.52	.67	.45	.55	.54	.60	.37	.53	.60
Weighted average R biserial/polyserial	.55	.52	.59	.53	.57	.63	.52	.51	.61	.62	.76	.56	.67
Weighted alpha reliability	.76	.73	.76	.72	.77	.76	.70	.72	.78	.77	.66	.53	.62
Weighted proportion of students attempting last item	.74	.77	.81	.73	.76	.83	.68	.81	.80	.88	.75	.91	.98
Nonpublic school
Unweighted sample size	300	300	300	200	300	200	300	200	200	200	200	200	200
Weighted average item score	.59	.49	.59	.45	.59	.72	.51	.60	.58	.66	.43	.56	.65
Weighted average R biserial/polyserial	.52	.49	.54	.55	.53	.62	.50	.50	.57	.62	.74	.59	.67
Weighted alpha reliability	.67	.67	.69	.74	.72	.70	.65	.69	.72	.72	.64	.55	.63
Weighted proportion of students attempting last item	.88	.88	.90	.75	.88	.93	.74	.88	.91	.93	.83	.95	.99

Block-level descriptive statistics as defined after univariate scaling, grade 4 science PBA national assessment, by block and school type: 2019
Statistic	Block S3	Block S4	Block S5	Block S6	Block S7	Block S8	Block S9	Block S10	Block S11
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.
The "Weighted proportion of students attempting last item" is equal to 1 – (Percent not responding to last item / 100). Weights are applied to reflect sampling design.
PBA = Paper-based assessment. The nonpublic school sample includes only private schools, including Catholic schools. BIE and DoDEA schools are not included in either the public or nonpublic category. Item statistics in this table are described on the page Blocks of Items.
U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2019 Science Assessment.
Number of scaled items	16	14	16	16	15	16	16	17	14
Public school
Unweighted sample size	2,200	2,100	2,100	2,100	2,000	2,100	2,100	2,000	2,000
Weighted average item score	.48	.55	.40	.55	.70	.45	.57	.49	.64
Weighted average R biserial/polyserial	.54	.59	.53	.56	.67	.49	.50	.51	.64
Weighted alpha reliability	.73	.76	.73	.77	.71	.69	.70	.73	.72
Weighted proportion of students attempting last item	.65	.79	.62	.67	.93	.56	.78	.67	.95
Nonpublic school
Unweighted sample size	200	200	200	200	200	200	200	200	200
Weighted average item score	.55	.60	.44	.63	.74	.48	.61	.56	.68
Weighted average R biserial/polyserial	.51	.55	.51	.53	.65	.49	.45	.46	.67
Weighted alpha reliability	.68	.65	.64	.72	.64	.64	.56	.65	.65
Weighted proportion of students attempting last item	.81	.94	.84	.85	.96	.67	.94	.81	.98

Block-level descriptive statistics as defined after multivariate scaling, grade 4 science DBA national assessment, by block and school type: 2019
Statistic	Block S2	Block S3	Block S4	Block S5	Block S6	Block S7	Block S8	Block S9	Block S10	Block S11	Block H2	Block I1	Block I3
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.
The "Weighted proportion of students attempting last item" is equal to 1 – (Percent not responding to last item / 100). Weights are applied to reflect sampling design.
DBA = Digitally based assessment. The nonpublic school sample includes only private schools, including Catholic schools. BIE and DoDEA schools are not included in either the public or nonpublic category. Item statistics in this table are described on the page Blocks of Items.
U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2019 Science Assessment.
Number of scaled items	16	17	16	17	16	17	15	17	16	17	5	10	7
Public school
Unweighted sample size	2,900	3,100	3,000	3,000	2,900	3,000	3,100	3,000	2,900	3,000	2,300	2,500	2,600
Weighted average item score	.52	.43	.54	.39	.52	.66	.43	.55	.55	.60	.37	.49	.60
Weighted average R biserial/polyserial	.55	.52	.58	.51	.56	.63	.52	.51	.60	.62	.76	.57	.67
Weighted alpha reliability	.76	.73	.76	.72	.77	.76	.71	.73	.78	.77	.66	.56	.62
Weighted proportion of students attempting last item	.74	.77	.81	.73	.76	.83	.68	.81	.80	.88	.75	.91	.98
Nonpublic school
Unweighted sample size	300	300	300	200	300	200	300	200	200	200	200	200	200
Weighted average item score	.58	.49	.60	.44	.59	.71	.49	.60	.59	.66	.43	.52	.65
Weighted average R biserial/polyserial	.52	.49	.53	.53	.53	.61	.50	.50	.57	.62	.74	.59	.67
Weighted alpha reliability	.66	.67	.69	.73	.72	.70	.66	.70	.72	.72	.64	.58	.63
Weighted proportion of students attempting last item	.88	.88	.90	.75	.88	.93	.74	.88	.91	.93	.83	.95	.99

Block-level descriptive statistics as defined after multivariate scaling, grade 4 science PBA national assessment, by block and school type: 2019
Statistic	Block S3	Block S4	Block S5	Block S6	Block S7	Block S8	Block S9	Block S10	Block S11
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.
The "Weighted proportion of students attempting last item" is equal to 1 – (Percent not responding to last item / 100). Weights are applied to reflect sampling design.
PBA = Paper-based assessment. The nonpublic school sample includes only private schools, including Catholic schools. BIE and DoDEA schools are not included in either the public or nonpublic category. Item statistics in this table are described on the page Blocks of Items.
U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2019 Science Assessment.
Number of scaled items	16	14	17	16	15	16	16	17	14
Public school
Unweighted sample size	2,200	2,100	2,100	2,100	2,000	2,100	2,100	2,000	2,000
Weighted average item score	.48	.56	.39	.55	.70	.45	.55	.50	.64
Weighted average R biserial/polyserial	.54	.58	.51	.56	.67	.49	.50	.50	.64
Weighted alpha reliability	.73	.75	.72	.77	.71	.69	.70	.74	.72
Weighted proportion of students attempting last item	.65	.79	.62	.67	.93	.56	.78	.67	.95
Nonpublic school
Unweighted sample size	200	200	200	200	200	200	200	200	200
Weighted average item score	.55	.61	.42	.63	.74	.48	.59	.58	.68
Weighted average R biserial/polyserial	.51	.54	.49	.53	.65	.49	.45	.46	.67
Weighted alpha reliability	.68	.65	.63	.72	.64	.64	.58	.67	.65
Weighted proportion of students attempting last item	.81	.94	.84	.85	.96	.67	.94	.81	.98

Last updated 05 October 2023 (SK)

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