Dose–response model of the form \[P(d) = \gamma + (1 - \gamma)(1 - e^{-\beta d^{\alpha}})\] where \(P(d)\) is the probability of a tumor (or other response) from lifetime, continuous exposure at dose \(d\) until age \(t\) (when tumor is fatal), \(\alpha\) is a fitted dose parameter (sometimes called the Weibull parameter), \(\beta\) is a fitted dose parameter, and \(\gamma\) is the background response rate.