|Statistic||Item type||All items|
|Number of scaled items||Total||20|
|Dichotomously scored constructed response||0|
|Polytomously scored constructed response||20|
|Unweighted sample size||†||144,200|
|Weighted average item score||†||0.52|
|Weighted average polyserial||†||0.90|
|Weighted alpha reliability||†||—|
|† Not applicable.
— In NAEP writing assessments, each block contains only one item — a writing prompt to which students respond with a polytomously scored constructed response; therefore, the weighted alpha reliability estimate is not meaningful.
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2002 Writing Assessment.