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philchalmers / faoutlier

Detecting outlying and influential cases for factor analysis in R

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Can I detect outliers even itemtype is 'nominal'?

seonghobae opened this issue · comments

commented

Hi, Phil
I saw the paper at 'Applied psychological measurement'. After that, I produce a silly question. Can I detect outliers for influential cases even item-type is nominal? I guess I can't do this, but I may find outliers even item-type is nominal.

Seongho

commented

Sure, but the problem is that categorical models often have next to no influence on fit because each item in isolation has little information. What would a univariate outlier look like on a categorical item: 5? 7? How much influence does this have on the model as a whole? So yes you can find them, but the odds are extremely low.

commented

My main consideration is relative with the 'Devide and Conquer' approach for the treat inaccuracy in Marginal Maximum Likelihood Estimation with EM/QMCEM; For the nominal response and non-sequential latent class model in mirt::mdirt() with unequal categories per item with type 'nominal responses'.

commented

I'd have to think about it, but this package is mostly about locating influential response patterns. So it's likely not what you want for comparing estimators.