Time and change: Using survival analysis in clinical assessment and treatment evaluation

Survival analysis is a set of statistical techniques that is useful for mod eling the types of changes commonly encountered in clinical assessment and treatment evaluation. This article provides a practical, comprehensive, mat hematically sound yet nontechnical introduction to survival methods. After discussing study design and data, a complete example data set from a fictit ious study of alcohol relapse patterns is introduced to illustrate commonly used survival analysis procedures, including the life-table method, the Ka plan-Meier procedure, the Cox proportional hazards model, and fully paramet ric survival models. These methods are used to describe the general surviva l and hazard functions, compare survival probabilities for groups of patien ts, develop multivariate hazard models, model the shape of the hazard funct ion over time, and use diagnostic tools to check statistical assumptions. C omplete SAS and SPSS programs are included in Appendix B.