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NAEP Analysis and Scaling → Initial Activities → Classical Item Analysis → Block-Level Descriptive Statistics by Public- and Nonpublic-School Sessions, as Defined After Scaling, Grade 12 Science National Main Assessment: 2005
Block-level descriptive statistics by public- and nonpublic-school sessions, as defined after scaling, grade 12 science national main assessment: 2005
Statistic Type of school1 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 6 16 8 8 16 11 17 16 15 13 13 13 9 16 15 13
Unweighted sample size Public 1,500 1,400 1,600 1,500 2,200 2,300 2,200 1,500 1,500 1,500 1,500 1,500 1,500 1,500 1,500 1,500
Nonpublic 400 400 400 400 600 600 500 400 400 400 400 400 400 400 400 400
Weighted average item score Public 0.49 0.41 0.63 0.49 0.37 0.63 0.54 0.43 0.48 0.54 0.47 0.42 0.34 0.44 0.42 0.40
Nonpublic 0.56 0.48 0.71 0.56 0.42 0.69 0.60 0.47 0.55 0.61 0.54 0.48 0.41 0.50 0.49 0.49
Weighted average polyserial Public 0.82 0.56 0.84 0.79 0.56 0.69 0.55 0.47 0.58 0.60 0.61 0.59 0.69 0.53 0.55 0.56
Nonpublic 0.80 0.58 0.79 0.79 0.54 0.67 0.54 0.49 0.63 0.60 0.58 0.58 0.63 0.53 0.54 0.55
Weighted alpha reliability Public 0.61 0.70 0.77 0.79 0.69 0.64 0.72 0.53 0.75 0.71 0.69 0.68 0.67 0.71 0.70 0.72
Nonpublic 0.55 0.70 0.71 0.78 0.68 0.54 0.69 0.57 0.77 0.68 0.65 0.67 0.63 0.69 0.67 0.70
Weighted proportion of students attempting last item2 Public 0.90 0.99 0.76 0.84 0.87 0.87 0.86 0.97 0.98 0.89 0.90 0.84 0.75 0.98 0.98 0.98
Nonpublic 0.95 0.99 0.84 0.88 0.93 0.94 0.91 0.97 0.98 0.96 0.95 0.92 0.79 0.98 0.98 0.99
† Not applicable.
1 Nonpublic-school sample includes only Catholic and private schools.
2 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 23 March 2009 (GF)

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