Goodness-of-fit plots and improvement within the basic model. Shown is an overview of the goodness-of-fit plots and the improvement of the basic model for rituximab after implementation of covariates (WT and sex). The solid line indicates the line of identity. Top graph shows the predicted (Pred) versus the observed concentrations (DV). The middle graph shows individual predictions (IPRED) versus observed concentrations (DV). The bottom graph shows population model predictions versus weighted residuals of the population model.