|Statistic||Item type||Block H3||Block H4||Block H5||Block H6||Block H7||Block H8|
|Number of scaled items||Total||16||16||15||16||16||17|
|Dichotomously scored constructed response||0||1||0||0||0||2|
|Polytomously scored constructed response||5||4||5||6||5||4|
|Unweighted sample size||†||2,200||2,200||2,100||2,100||2,200||2,100|
|Weighted average item score||†||0.43||0.45||0.48||0.41||0.45||0.43|
|Weighted average polyserial||†||0.49||0.52||0.51||0.54||0.47||0.48|
|Weighted alpha reliability||†||0.75||0.72||0.72||0.74||0.69||0.68|
|Weighted proportion of students attempting last item1||†||0.72||0.84||0.89||0.74||0.72||0.81|
|† Not applicable.
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), 2006 U.S. History Assessment.