02-16-2016 02:35 PM
I am still working on an item response theory (IRT) analysis to find differential item functioning (DIF) in any of the items of a 17-item graded response likert scale.
02-17-2016 12:49 PM
My question is this: is your concern over a negative log likelihood (which happens a lot) or over a negative difference, such that the difference (more complex model minus less complex model) is uninterpretable? Examples, with explanations, would help.
02-17-2016 02:51 PM
Many SAS procedures print -2LL as a convenience, since one just has to subtract values without remembering to multiply by 2 or -2. The smaller the -2LL, the better the fit (ignoring the differneces in parameter numbers). The LRT is just the difference.