The log-normal senescent model indicates that platelet life span is internally controlled. (A) Monte Carlo bootstrap resampling was performed to generate estimates of the best-fit model parameters for wild-type, Bcl-x^+/Plt20, and Bak^−/− mice. m indicates mean log life span; and s, SD of log life span (20 samples; horizontal line and error bars represent median and interquartile range). The quality of fits was very similar to those obtained with the multiple-hit model (supplemental Figure 3). The differences between any 2 genotypes are statistically significant (P < .001, 2-tailed unpaired t test) for either parameter; however, the magnitudes of the differences are clearly greater in the mean of log life span. (B) Best-fit log-normal life span distributions with time on a log scale. (C) Best-fit log-normal life span distributions with time on a linear scale. Numerical values for the best-fit model parameters are reported in supplemental Table 2.