Table 3. Pharmacokinetic Model Selection Criteria for Four Illustrative Model Fits

CCV = constant coefficient of variability model; SBC = Schwartz-Bayesian Criterion; AIC = Akaike’s Information Criterion; LRT (P value) = P values from the Likelihood Ratio Test, which can only be used to compare nested models. These P-values compare the model with the model immediately to its left.

−2LL =−2 · log (likelihood) is the objective function minimized by NONMEM during model fitting of parameter estimates. −2LL, AIC and LRT (P value) are included for readers more familiar with these model selection criteria. SBC is the most parsimonious in adding model parameters and thus our basis for model selection.