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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 Combined National and State Main Assessment: 2005
Overall descriptive statistics for item blocks as defined after scaling, grade 8 science combined national and state main assessment: 2005
Statistic Item type Block S3 Block S4 Block S5 Block S6 Block S7 Block S8 Block S9 Block S10 Block S11 Block S12 Block S13 Block S14 Block S15 Block S16 Block S17 Block S18
Number of scaled items Total 6 18 8 7 17 9 13 19 15 14 15 15 17 14 18 18
Multiple choice 0 12 0 0 12 5 6 14 10 8 7 7 11 10 12 12
Dichotomously scored constructed response 3 1 4 4 2 1 3 2 2 1 3 2 0 1 1 0
Polytomously scored constructed response 3 5 4 3 3 3 4 3 3 5 5 6 6 3 5 6
Unweighted sample size 21,200 19,600 21,000 21,600 29,400 29,700 29,600 20,100 20,300 19,800 19,700 19,700 19,500 19,600 19,600 19,600
Weighted average item score 0.49 0.42 0.47 0.38 0.47 0.58 0.55 0.50 0.37 0.41 0.48 0.39 0.51 0.47 0.54 0.48
Weighted average polyserial 0.74 0.50 0.79 0.81 0.52 0.72 0.62 0.53 0.55 0.50 0.56 0.55 0.53 0.55 0.53 0.52
Weighted alpha reliability 0.70 0.66 0.73 0.50 0.67 0.65 0.72 0.74 0.70 0.63 0.72 0.70 0.72 0.69 0.75 0.75
Weighted proportion of students attempting last item1 0.77 0.93 0.55 0.85 0.85 0.95 0.96 0.98 0.98 0.91 0.95 0.83 0.96 0.99 0.99 0.92
† Not applicable.
1 The "Weighted proportion of students attempting last item" is equal to 1 - (Percent not responding to last item /100).
NOTE: 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), 2005 Science Assessment.

Last updated 17 February 2010 (GF)

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