Hi there,
This should be a quick question considering it is probably common knowledge for all of you. I am looking for some clarification regarding the mxcompare output. Just to be certain, is "diffll" synonymous with chi-squared? From the openmx user guide I cannot see where else a chi-square output would be located. If this is not the case, how can one determine the chi-square value from the usual mxcompare output?
Thank you in advance and please excuse my extreme naivety.
diffll is the difference in model minus2LL. See ?mxRefModels
The chi-sq stat is generally the saturated model vs the candidate model. For example,
Is saying the same thing as,
Jpritikin,
I appreciate your response in regards to my question! This helps clear up so much for me. Best wishes.
Asymptotically, under certain regularity conditions (Steiger et al 1985) the difference in -2lnL between a model and a submodel of it (created by equating parameters or fixing them at specific values) is distributed as chi-squared with df equal to the difference in the number of free parameters.
Various things can disrupt the regularity conditions. Mixture distributions, parameter bounds, non-linear constraints to maintain positive definiteness are some of them.
Thank you very much for the clarification, Dr. Neale!