We've got a 524*40 data frame of responses to a likert-type scale questionnaire (7 response categories on 40 items). We want to do exploratory multidimensional IRT using the MHRM method to identify the latent structure. When we run
mirt(SAQdata3, 4, method = 'MHRM')
we get the following error message:
Stage 1: Cycle = 1, Log-Lik = -46764.0, Max Change = 0.2500 Stage 1: Cycle = 2, Log-Lik = -45091.4, Max Change = 0.2500 Error in solve.default(ave.h, grad) : system is computationally singular: reciprocal condition number = 7.06167e-20
We understand that there's something going wrong with the optimization method due to the structure of the data but are unclear exactly what is wrong and if there is any way to fix it?