Survival Analysis Overview
Survival data need to be analyzed with specialized methods for two reasons:
1. The survival times usually have specialized non-normal distributions, like the exponential, Weibull, and lognormal.
2. Some of the data could be censored.
Survival functions are calculated using the nonparametric Kaplan-Meier method for one or more groups of either complete or right-censored data. Complete data have no censored values. Right-censoring is when you do not know the exact survival time, but you know that it is greater than the specified value. Right-censoring occurs when the study ends without all the units failing, or when a patient has to leave the study before it is finished. The censored observations cannot be ignored without ...