ABSTRACT
In some studies, the response variable of interest is the amount of time from an initial observation until the occurrence of a subsequent event. Examples include the time from birth until death, the time from transplant surgery until the new organ fails, and the time from the start of maintenance therapy for a patient whose cancer has gone into remission until the relapse of disease. This time interval between a starting point and a subsequent event, often called a failure, is known as the survival time. Although the measurements of survival times are continuous, their distributions are rarely normal; instead, they tend to be skewed to the right. The analysis of this type of data generally focuses on estimating the probability that an individual will survive for a given length of time.
