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NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Overall Descriptive Statistics for Item Blocks as Defined After Scaling, Grade 12 Science National Assessment, by Block: 2019

​​NAEP Technical DocumentationOverall Descriptive Statistics for Item Blocks as Defined After Scaling, Grade 12 Science National Assessment, by Block: 2019

Overall descriptive statistics for item blocks as defined after univariate scaling, grade 12 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 S13 Block H1 Block H3 Block I1 Block I2 Block I5
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 19 17 17 18 18 17 19 19 18 15 16 18 4 7 6 5 11
Number of multiple-choice items 13 11 12 10 12 11 14 16 12 10 11 11 0 0 0 2 0
Number of dichotomously scored CR items 2 1 0 2 1 2 1 0 3 1 1 4 1 4 3 1 1
Number of polytomously scored CR items 4 5 5 6 5 4 4 3 3 4 4 3 3 3 3 2 10
Unweighted sample size 2,200 2,300 2,300 2,300 2,200 2,300 2,300 2,300 2,300 2,300 2,200 2,300 1,800 1,800 1,900 1,900 1,900
Weighted average item score .44 .44 .45 .42 .41 .42 .45 .51 .49 .43 .43 .42 .39 .54 .41 .41 .48
Weighted average R biserial/polyserial .60 .58 .57 .58 .58 .58 .56 .57 .57 .62 .56 .59 .79 .70 .70 .70 .71
Weighted alpha reliability .79 .77 .75 .79 .78 .77 .79 .80 .77 .75 .72 .78 .53 .59 .60 .39 .79
Weighted proportion of students attempting last item .95 .94 .94 .96 .95 .96 .95 .95 .96 .97 .96 .96 .90 .72 .95 .99 .97
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Overall descriptive statistics for item blocks as defined after univariate scaling, grade 12 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 Block S13
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 17 16 17 17 16 17 19 17 16 14 14
Number of multiple-choice items 11 11 12 12 10 11 16 13 11 9 9
Number of dichotomously scored CR items 1 1 2 1 1 1 0 2 1 0 0
Number of polytomously scored CR items 5 4 3 4 5 5 3 2 4 5 5
Unweighted sample size 1,600 1,700 1,700 1,700 1,600 1,700 1,600 1,600 1,600 1,700 1,700
Weighted average item score .44 .43 .41 .42 .44 .45 .53 .54 .46 .42 .41
Weighted average R biserial/polyserial .58 .60 .52 .57 .59 .61 .59 .56 .60 .55 .57
Weighted alpha reliability .79 .77 .70 .77 .78 .80 .81 .75 .75 .67 .74
Weighted proportion of students attempting last item .87 .89 .90 .87 .93 .93 .91 .93 .93 .95 .89
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Overall descriptive statistics for item blocks as defined after multivariate scaling, grade 12 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 S13 Block H1 Block H3 Block I1 Block I2 Block I5
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 19 17 18 18 19 18 19 19 18 17 17 18 4 8 6 5 11
Number of multiple-choice items 13 11 13 10 13 12 14 16 12 12 12 11 0 1 0 2 0
Number of dichotomously scored CR items 2 1 0 2 1 2 0 0 3 0 0 4 0 4 3 1 1
Number of polytomously scored CR items 4 5 5 6 5 4 5 3 3 5 5 3 4 3 3 2 10
Unweighted sample size 2,200 2,300 2,300 2,300 2,200 2,300 2,300 2,300 2,300 2,300 2,200 2,300 1,800 1,800 1,900 1,900 1,900
Weighted average item score .44 .45 .45 .42 .41 .41 .46 .51 .50 .41 .43 .42 .41 .53 .41 .46 .48
Weighted average R biserial/polyserial .60 .58 .55 .58 .56 .57 .56 .57 .57 .57 .55 .59 .78 .65 .69 .70 .71
Weighted alpha reliability .79 .77 .75 .79 .77 .77 .79 .79 .77 .74 .74 .78 .57 .60 .61 .42 .79
Weighted proportion of students attempting last item .95 .94 .94 .96 .90 .95 .95 .95 .96 .97 .96 .96 .90 .72 .95 .99 .97
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Overall descriptive statistics for item blocks as defined after multivariate scaling, grade 12 science PBA national assessment, by block: 2019
StatisticBlock S3Block S4Block S5Block S6Block S7Block S8Block S9Block S10Block S11Block S12Block S13
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 items1718171717171917161515
Number of multiple-choice items1113121211111613111010
Number of dichotomously scored CR items10211001000
Number of polytomously scored CR items55345633555
Unweighted sample size1,6001,7001,7001,7001,6001,7001,6001,6001,6001,7001,700
Weighted average item score.45.44.41.40.44.44.53.53.44.40.40
Weighted average R biserial/polyserial.58.55.52.56.57.61.59.55.60.53.56
Weighted alpha reliability.78.76.70.76.77.81.80.75.75.67.74
Weighted proportion of students attempting last item.87.89.90.87.93.93.91.93.93.95.89
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Last updated 05 October 2023 (SK)