|Statistic||Item type||Block G3||Block G4||Block G5||Block G6||Block G7||Block G8||Block G9|
|Number of scaled items||Total||16||17||17||16||15||16||22|
|Dichotomously scored constructed response||0||0||2||0||0||1||3|
|Polytomously scored constructed response||5||5||4||4||4||5||4|
|Unweighted sample size||2,300||2,300||2,200||2,300||2,300||2,300||2,300|
|Weighted average item score||0.55||0.49||0.65||0.56||0.44||0.38||0.51|
|Weighted average polyserial||0.60||0.53||0.64||0.56||0.55||0.60||0.59|
|Weighted alpha reliability||0.75||0.75||0.80||0.76||0.72||0.76||0.81|
|Weighted proportion of students attempting last item1||0.95||0.88||0.98||0.94||0.60||0.74||0.99|
|1The "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.