The presence of biased items may seriously affect
methods used to link metrics in item response theory.
An iterative procedure designed to minimize this
methodological problem was examined in a monte
carlo investigation using the two-parameter item response
model. The iterative procedure links the scales
of independently calibrated parameter estimates using
only those items identified as unbiased. Two methods
for transforming parameter estimates to a common
metric were incorporated into the iterative procedure.
The first method links scales by equating the first two
moments of the distributions of estimated item difficulties.
The second method determines the linking
transformation by minimizing differences across IRT
characteristic curve estimates. Results indicate that iterative
linking provides a substantial improvement in
item bias detection over the noniterative approach.
Index terms: Item bias, Item response theory, Iterative
method, Linking, Metric linking, Two-parameter item
Candell, Gregory L.; Drasgow, Fritz.
An iterative procedure for linking metrics and assessing item bias in item response theory.
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