|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||2||1||0||0||0||2|
|Polytomously scored constructed response||4||4||5||5||5||4|
|Unweighted sample size||2,400||2,400||2,500||2,500||2,400||2,400|
|Weighted average item score||0.44||0.45||0.47||0.46||0.44||0.42|
|Weighted average polyserial||0.49||0.53||0.54||0.52||0.47||0.50|
|Weighted alpha reliability||0.65||0.73||0.73||0.72||0.68||0.69|
|Weighted proportion of students attempting last item1||0.84||0.83||0.92||0.76||0.69||0.84|
|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 U.S. History Assessment.