On page 3130 of the SAS 9.2 Proc Lifetest user's guide, the median survival time is defined as the minimum time in which the survival probability is less than but does not include 50%.   What I learned from graduate school and online sources is that median survival time is the minimum time in which the survival probability is less than or equal to 50%.   Why does SAS define median survival time as when survival probability is less than 50% while other sources define median survival time as less than or equal to 50%?   ... View more