Statistic | Type of School1 | Block S3 | Block S4 | Block S5 | Block S6 | Block S7 | Block S8 | Block S9 | Block S10 | Block S11 | Block S12 |
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† 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: Univariate scale. 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), 2009 Science Assessment. |
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Number of scaled items | † | 15 | 18 | 18 | 17 | 15 | 18 | 13 | 17 | 16 | 15 |
Unweighted sample size | Public | 29,500 | 29,400 | 29,300 | 29,300 | 29,200 | 29,300 | 29,100 | 29,100 | 29,100 | 29,100 |
Nonpublic | 600 | 600 | 600 | 600 | 600 | 600 | 600 | 600 | 600 | 600 | |
Weighted average item score | Public | 0.54 | 0.48 | 0.46 | 0.47 | 0.41 | 0.46 | 0.41 | 0.52 | 0.40 | 0.44 |
Nonpublic | 0.61 | 0.54 | 0.54 | 0.53 | 0.47 | 0.53 | 0.47 | 0.58 | 0.47 | 0.52 | |
Weighted average polyserial | Public | 0.52 | 0.53 | 0.51 | 0.52 | 0.54 | 0.54 | 0.58 | 0.57 | 0.54 | 0.57 |
Nonpublic | 0.48 | 0.48 | 0.51 | 0.47 | 0.50 | 0.51 | 0.57 | 0.54 | 0.50 | 0.53 | |
Weighted alpha reliability | Public | 0.73 | 0.74 | 0.74 | 0.75 | 0.73 | 0.74 | 0.71 | 0.78 | 0.73 | 0.75 |
Nonpublic | 0.67 | 0.66 | 0.71 | 0.67 | 0.67 | 0.69 | 0.69 | 0.73 | 0.70 | 0.68 | |
Weighted proportion of students attempting last item2 | Public | 0.89 | 0.82 | 0.88 | 0.90 | 0.77 | 0.90 | 0.94 | 0.80 | 0.76 | 0.84 |
Nonpublic | 0.90 | 0.87 | 0.94 | 0.94 | 0.77 | 0.93 | 0.96 | 0.85 | 0.77 | 0.88 |