|Statistic||Item type||Block G3||Block G4||Block G5||Block G6||Block G7||Block G8|
|Number of scaled items||Total||15||15||14||15||14||17|
|Dichotomously scored constructed response||1||3||2||0||2||3|
|Polytomously scored constructed response||4||2||2||5||2||2|
|Unweighted sample size||2,500||2,400||2,400||2,400||2,400||2,400|
|Weighted average item score||0.53||0.58||0.57||0.48||0.49||0.44|
|Weighted average polyserial||0.58||0.58||0.59||0.54||0.63||0.51|
|Weighted alpha reliability||0.77||0.76||0.73||0.73||0.79||0.68|
|Weighted proportion of students attempting last item1||0.87||0.95||0.92||0.87||0.62||0.80|
|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), 2001 Geography Assessment.