Simulated data were used to investigate systematically
the impact of various orderings of step difficulties
on the distribution of item information for the partial
credit model. It was found that the distribution of
information for an item was a function of (1) the
range of the step difficulty values, (2) the number of
step difficulties that were out of sequential order, and
(3) the distance between the step values that were out
of order. Also, by using relative efficiency comparisons,
the relationship between the step estimates and
the distribution of item information was used to demonstrate
the effects of various test revisions (through
the addition and/or deletion of items with specific step
characteristics) on the resulting test’s precision of
measurement. The usefulness of item and test information
functions for specific measurement applications
of the partial credit model is also discussed.
Dodd, Barbara G.; Koch, William R..
Effects of variations in item step values on item and test information in the partial credit model.
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