Basic goodness of fit plots for PK and PD models. (A) and (B) are goodness of fit plots for PK (IFN-α) and PD (neopterin) models, respectively. Black line, line of identity; gray line, LOESS (locally weighted regression) smooth line. The encircled dots in the PD plots represent one outlier (ID No. 2) whose IFN-α concentrations were very low, but whose neopterin concentrations were rather higher.