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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 Science National Assessment, by Block: 2019

​​NAEP Technical DocumentationOverall Descriptive Statistics for Item Blocks as Defined After Scaling, Grade 8 Science National Assessment, by Block: 2019

Overall descriptive statistics for item blocks as defined after univariate scaling, grade 8 science DBA national assessment, by block: 2019
Statistic Block S2 Block S3 Block S4 Block S5 Block S6 Block S7 Block S8 Block S9 Block S10 Block S11 Block S12 Block H1 Block I1 Block I4
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. CR = Constructed response. 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.
Total number of scaled items 17 16 18 16 17 18 18 17 18 16 14 4 11 6
Number of multiple-choice items 10 11 13 10 11 11 13 12 14 11 8 0 2 1
Number of dichotomously scored CR items 3 0 1 1 1 4 1 1 2 0 2 1 5 0
Number of polytomously scored CR items 4 5 4 5 5 3 4 4 2 5 4 3 4 5
Unweighted sample size 2,900 3,000 3,000 3,000 3,100 2,900 2,900 2,900 3,000 2,900 3,000 2,300 3,100 3,300
Weighted average item score .55 .54 .51 .46 .50 .57 .48 .51 .57 .53 .45 .49 .51 .40
Weighted average R biserial/polyserial .57 .51 .53 .58 .51 .60 .54 .56 .58 .60 .59 .87 .63 .68
Weighted alpha reliability .76 .73 .74 .75 .75 .79 .75 .76 .78 .79 .75 .67 .70 .62
Weighted proportion of students attempting last item .92 .89 .82 .94 .91 .91 .90 .94 .89 .90 .86 .73 .97 .93
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Overall descriptive statistics for item blocks as defined after univariate scaling, grade 8 science PBA national assessment, by block: 2019
Statistic Block S3 Block S4 Block S5 Block S6 Block S7 Block S8 Block S9 Block S10 Block S11 Block S12
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. CR = Constructed response. 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.
Total number of scaled items 16 18 18 17 15 18 13 17 16 15
Number of multiple-choice items 11 13 13 11 9 13 7 14 12 9
Number of dichotomously scored CR items 0 0 0 0 0 1 1 3 0 2
Number of polytomously scored CR items 5 5 5 6 6 4 5 0 4 4
Unweighted sample size 2,100 2,200 2,200 2,200 2,100 2,100 2,100 2,100 2,100 2,100
Weighted average item score .55 .51 .49 .50 .42 .50 .43 .61 .58 .45
Weighted average R biserial/polyserial .49 .53 .51 .51 .55 .54 .61 .61 .60 .55
Weighted alpha reliability .72 .75 .76 .76 .75 .75 .75 .78 .78 .74
Weighted proportion of students attempting last item .80 .70 .78 .81 .63 .83 .88 .91 .87 .72
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Overall descriptive statistics for item blocks as defined after multivariate scaling, grade 8 science DBA national assessment, by block: 2019
Statistic Block S2 Block S3 Block S4 Block S5 Block S6 Block S7 Block S8 Block S9 Block S10 Block S11 Block S12 Block H1 Block I1 Block I4
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. CR = Constructed response. 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.
Total number of scaled items 17 16 18 16 17 18 18 17 18 17 15 4 11 6
Number of multiple-choice items 10 11 13 10 11 11 13 12 14 12 9 0 2 1
Number of dichotomously scored CR items 3 0 0 0 0 4 1 0 1 0 1 0 5 0
Number of polytomously scored CR items 4 5 5 6 6 3 4 5 3 5 5 4 4 5
Unweighted sample size 2,900 3,000 3,000 3,000 3,100 2,900 2,900 2,900 3,000 2,900 3,000 2,300 3,100 3,300
Weighted average item score .55 .54 .50 .47 .49 .57 .48 .51 .57 .54 .43 .59 .51 .42
Weighted average R biserial/polyserial .57 .51 .52 .57 .51 .60 .54 .56 .58 .59 .56 .82 .63 .68
Weighted alpha reliability .76 .73 .74 .76 .75 .79 .75 .76 .78 .78 .75 .69 .70 .61
Weighted proportion of students attempting last item .92 .89 .82 .94 .91 .91 .90 .94 .89 .90 .86 .73 .97 .93
​

Overall descriptive statistics for item blocks as defined after multivariate scaling, grade 8 science PBA national assessment, by block: 2019
StatisticBlock S3Block S4Block S5Block S6Block S7Block S8Block S9Block S10Block S11Block S12
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. CR = Constructed response. 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.
Total number of scaled items16181817151813171615
Number of multiple-choice items11131311913714129
Number of dichotomously scored CR items0000010300
Number of polytomously scored CR items5556646046
Unweighted sample size2,1002,2002,2002,2002,1002,1002,1002,1002,1002,100
Weighted average item score.55.51.49.50.42.50.44.61.58.42
Weighted average R biserial/polyserial.49.53.51.51.55.54.61.61.60.55
Weighted alpha reliability.73.75.76.76.75.75.75.78.78.74
Weighted proportion of students attempting last item.80.70.78.81.63.83.88.91.87.72
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Last updated 05 October 2023 (SK)