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philchalmers / mirt

Multidimensional item response theory
https://philchalmers.github.io/mirt/
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Estimating 3PL with fixed guessing parameter #239

Closed ghost closed 1 year ago

ghost commented 1 year ago

Hi, when I estimating 3PL with fixed guessing parameter, using function mirt() leads to estimated guessing parameter in result. mod.3PLwithFGP = mirt(data = dat, model = 1, itemtype = "3PL", guess = 0.25) Or is estimating 3PL with fixed guessing parameter must be down via user defined function using createItem()?

philchalmers commented 1 year ago

Use itemtype = '2PL' if you don't want the lower-asymptote parameter to be estimated. The guess vector is just a set of starting values.