Fig. 2. Ratio of measured to predicted propofol concentrations versus time for the elderly patients (aged > 65 yr) of the Schüttler and Ihmsen 1data set who were administered propofol as a continuous infusion. Predictions were calculated with (A ) the Schüttler and Ihmsen 1parameter set and (B ) the Schnider et al. 3parameter set. Conc. = concentration; MWR = median weighted residual; MAWR = median absolute weighted residual, with the single residual calculated as (measured concentration − predicted concentration)/predicted concentration.