exploratory within item multidimensional IRT models

[Asghar Minaei]

Hello Phil,

I am currently working on an exploratory within item multidimensional IRT analysis. When I ran my analysis, I noticed that the slope parameters (*a*) of all items across the three dimensions were negative. This issue often occurs due to the default identification constraints used by the mirt software, and  one way to address it is to change the default settings.

Could you kindly explain how I can modify the default identification constraints in the *mirt* package for an exploratory within item multidimensional analysis? Your guidance would be extremely helpful to me. My codes are:

fit_compensatory <- mirt(data = data, model = 3,

                 itemtype = "2PL", method = "MHRM", 

                 SE = TRUE, rotate="oblimin")

                 

extract.mirt(fit_compensatory, what="converged")

params <- coef(fit_compensatory, simplify = TRUE)

M2(fit_compensatory)

With best regards,

Asghar