In some studies, the outcome of interest is the time until some event occurs: readmission to hospital, the next manic episode, or even death. Survival analysis is a techique which can be used to analyze such data. It has added usefulness because it allows us to use data from subjects who drop out of sight over the course of the follow-up period as well as from those who do not experience the event by the time the study ends. This article introduces this technique and provides some guidelines for designing follow-up trials.
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