Survival analysis is a class of statistical methods for studying the occurrence and timing of events. These methods ar most often applied to the study of deaths. In fact, they were originally designed for that purpose, which explains the name survival analysis. That name is somewhat unfortunate, however, because it encourages a highly restricted view of the potential applications of these methods. Survival analysis is extremely useful for studying many different kinds of events in both the social and natural sciences, including the onset of disease, equipment failures, earthquakes, automobile accidents, stock market crahes, revoluations, job terminations, births, marriges, divorces, promotions, retirements and arrests. Because these methods have been adapted - and sometimes independently discovered - by researchers in several different fields, they also go by several different names: event history analysis (sociology), reliability analysis and failure time analysis (engineering), duration and transition analysis (u.a. developmental psychology, economics).