|Statistic||Item type||Block H3||Block H4||Block H5||Block H6||Block H7||Block H8|
|Number of scaled items||Total||14||16||15||15||16||17|
|Dichotomously scored constructed response||1||1||0||0||0||2|
|Polytomously scored constructed response||5||4||5||5||5||4|
|Unweighted sample size||2,400||2,300||2,300||2,300||2,300||2,300|
|Weighted average item score||0.43||0.46||0.48||0.48||0.44||0.43|
|Weighted average polyserial||0.49||0.53||0.54||0.51||0.47||0.49|
|Weighted alpha reliability||0.64||0.73||0.74||0.72||0.68||0.69|
|Weighted proportion of students attempting last item1||0.84||0.83||0.91||0.76||0.68||0.83|
|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 U.S. History Assessment.