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philchalmers / mirt

Multidimensional item response theory
https://philchalmers.github.io/mirt/
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bfactor and MHRM #192

Closed Pip-griff closed 4 years ago

Pip-griff commented 4 years ago

Hi Phil, I may be wrong here (and I am not sure this is an issue as such), but it seems that the bfactor model cannot be set up to use model = "MHRM". I have tried running a longitudinal IRT model with between 3 and 7 timepoints in mirt and the quadrature is an issue. Either quadrature is is too low to reach a solution, or too high for memory allocation.

Could bfactor be set up to include MHRM, or is there something which would prevent stochastic methods here?

thanks! Pip

philchalmers commented 4 years ago

Thanks, Pip. This is actually by design since bfactor() provides a specific data-reduction integration approach that doesn't generalize to everything else that mirt supports; hence, this function has been isolated from the more central mirt() function. That said, you can reproduce the fitted bfactor() models in mirt() just by specifying a suitable syntax and using the 'MHRM' algorithm as you've requested.

Pip-griff commented 4 years ago

Thanks for this Phil,

I have now found the google groups and I will post there in future.

Now I am off to try and build the model in mirt()