How is model fit assessed? How does one compare different models for the same data?
Model fit is assessed by comparing the observed crossclassification frequencies to the expected frequencies predicted by the model. The difference is formally assessed with a likelihood ratio (LR) chi-squared statistic; by convention, this is denoted by G² (G-squared). The G² statistic is similar to, but calculated somewhat differently from than the more familiar Pearson chi-squared (X² or X-squared) statistic.
