Measures of relative model fit

Most software for statistical model fitting reports the value of the maximized log likelihood function, but the numerical value is difficult to interpret because of its log scale, its dependence on the sample size, and the possible omission of constants. A sample-size-scaled version of the likelihood function summarizes the model fit. A related index uses the mean of the contributions to the likelihood function. The ratio or difference of either index for two models is a summary measure of relative model fit. We discuss these measures and briefly consider interval estimation for them. (C) 2002 Elsevier Science B.V. All rights reserved.