Fig. 3. A contour plot (A ) and a three-dimensional bivariate joint probability distribution function (B ) from 3,347,523 pharmacokinetically censored data points from 1,100 patients over an end tidal anesthetic concentration (ETAC) range from 0.42 to 1.51 age-adjusted minimum alveolar concentration (MAC) during anesthetic maintenance. The median was 1,883 data points from individual patients (range, 1 to 26,140). These plots demonstrate that for a given age-adjusted MAC, the response variable (i.e. , bispectral index value) displays its highest densities in the low 40s. The mode density of bispectral index values remains in the low 40s over the ETAC range from 0.42 to 1.51 age-adjusted MAC (more than 98% of the ETAC data).