Figure 5. This "parallel plot" shows the association between R²and the plasma effect-site equilibration rate constant (k^e0) and the other pharmacodynamic parameters. The x axis represents the proportional value of each estimate to the smallest and largest values, which define the left and right edges, respectively. The k^e0estimates are not biased by high or low R²values. R²represents the signal:noise ratio. The parameters that are significantly correlated with age have less variability than do the others.