Covariance estimation based on asymptotic normal estimating function

Survival analysis is the analysis of data that corresponds to the time from a welldefined origin of time until the occurrence of some particular event or end point. In medical research, the origin of fime could be the time of birth, or the recruitment of an individual into an experiment study, such as clinical trial to compare two or more treatments. If the end point is the death of a patient, the resulting data are literally survival times.

The two-sample accelerated life model has been a general model for comparing censored survival times from two groups. This model assumes that the survival time of an individual in one group is distributed as a multiple of the survival time of an individual in the other group. Therefore, the probability of an individual on the new treatment surviving over time is the probability of an individual under the standard treatment surviving over time 01, where ^ is an unknown positive scale.