|Statistic||Item type||Block G3||Block G4||Block G5||Block G6||Block G7||Block G8||Block G9|
|Number of scaled items||Total||17||16||17||16||14||17||25|
|Dichotomously scored constructed response||0||1||2||0||0||2||3|
|Polytomously scored constructed response||5||4||4||4||4||3||7|
|Unweighted sample size||2,300||2,300||2,300||2,300||2,300||2,300||2,400|
|Weighted average item score||0.49||0.52||0.49||0.40||0.44||0.67||0.50|
|Weighted average polyserial||0.58||0.50||0.61||0.50||0.58||0.62||0.53|
|Weighted alpha reliability||0.77||0.68||0.79||0.69||0.74||0.77||0.80|
|Weighted proportion of students attempting last item1||0.98||0.97||0.97||0.91||0.73||0.94||0.99|
|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.