摘要：In its standard form, a lifetime regression model usually assumes that the time until an
event occurs has a constant shape parameter and a scale parameter that is a function of
covariates. In this paper we consider lifetime models with shape parameter dependent
on a vector of covariates. Two special models are considered, the Weibull model and a
mixture model incorporating long-term survivors, when we consider that the incidence
probability is also dependent on covariates. Classical parameters estimation approach
is considered on two real data sets.
