Fig. 3. These histograms display the minimum alveolar concentration (MAC) values obtained in 500 replicates. The increment size between concentration changes was 20% of the starting concentration. In the upper panel, the starting concentration for each replicate was 0.5% (with an increment size of 0.1%); in the lower panel, the starting concentration for each replicate was 1.5% (with an increment size of 0.3%). The lower starting concentration produced a slight bias toward smaller estimates for MAC (60% of values were < 1.0%). Because increment size is a function of the starting concentration, increment size for the lower panel is larger, presumably explaining gaps in the distribution in that panel.