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NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Block-Level Descriptive Statistics as Defined After Scaling, Grade 8 Geography National Assessment, by Block and School Type: 2018

NAEP Technical DocumentationBlock-Level Descriptive Statistics as Defined After Scaling, Grade 8 Geography National Assessment, by Block and School Type: 2018

Block-level descriptive statistics as defined after scaling, grade 8 geography DBA national assessment, by block and school type: 2018
StatisticType of school1Block G1Block G2Block G3Block G4Block G5Block G6Block G7
Number of scaled items†20
20
20
20
19
21
23
Unweighted sample sizePublic1,7001,7001,7001,7001,7001,7001,600
Nonpublic100100200100100200200
Weighted average item score2Public.53.44.51.49.49.56.58
Nonpublic.62.49.57.55.56.63.63
Weighted average polyserialPublic.53.46.53.47.51.52.56
Nonpublic.50.50.49.45.55.56.59
Weighted alpha reliabilityPublic.77.70.76.73.76.77.83
Nonpublic.69.73.72.67.77.78.83
Weighted proportion of students attempting last item3Public.94.89.90.86.86.95.88
Nonpublic.98.96.97.94.99.99.93
† Not applicable.
1 Nonpublic school sample includes only private schools, including Catholic schools. BIE and DoDEA schools are not included in either the public or nonpublic category.
2 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.
3 The "Weighted proportion of students attempting last item" is equal to 1 – (Percent not responding to last item / 100).
NOTE: DBA = Digitally based assessment. Item statistics in this table are described on the page Blocks of Items. The block naming conventions used in this table are described in the document 2018 Block Naming Conventions in Data Products and TDW PDF File .
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2018 Geography Assessment.
Block-level descriptive statistics as defined after scaling, grade 8 geography PBA national assessment, by block and school type: 2018
StatisticType of school1Block G3Block G4Block G5Block G6Block G7Block G8Block G9
Number of scaled items†17161516151725
Unweighted sample sizePublic1,5001,5001,5001,6001,5001,5001,400
Nonpublic100100100100100100100
Weighted average item score2Public.48.49.49.39.54.44.52
Nonpublic.55.52.58.46.59.51.60
Weighted average polyserialPublic.57.49.56.51.59.50.53
Nonpublic.50.51.56.48.62.46.50
Weighted alpha reliabilityPublic.75.69.75.72.74.71.80
Nonpublic.62.69.72.66.77.62.80
Weighted proportion of students attempting last item3Public.92.90.88.82.66.88.97
Nonpublic.98.99.91.93.79.951.00
† Not applicable.
1 Nonpublic school sample includes only private schools, including Catholic schools. BIE and DoDEA schools are not included in either the public or nonpublic category.
2 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.
3 The "Weighted proportion of students attempting last item" is equal to 1 – (Percent not responding to last item / 100).
NOTE: PBA = Paper-based assessment. Item statistics in this table are described on the page Blocks of Items. The block naming conventions used in this table are described in the document 2018 Block Naming Conventions in Data Products and TDW PDF File .
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2018 Geography Assessment.

Last updated 19 December 2022 (PG)