Y:\GAIN\Eval Team\Analytic Training Series Memos\Final_onWeb\Survival Analysis.doc 1 LI Analysis Training Series Survival Analysis/Life Tables (Last Revised: 4/17/2007 (2/17/2000))

Acknowledgement: This document was developed under contract #270-2003-00006 from the Substance Abuse and Mental Health Services Administration (SAMHSA’s) Center for Substance Abuse Treatment (CSAT). Any opinions about this data are those of the authors and do not represent official positions of the government or individual grantees. Purpose: Survival analysis, including Life Tables and Hazard analysis, is a way of examining the time to an event (e.g., discharge, admission/readmission, symptom onset, task completion, death) for one or more groups. Survival analysis considers not simply whether an event might occur, but also considers when it might occur (See Willett and Singer, 1991). It accounts for cases where data about the terminal event is unavailable (censored) due to client attrition or study cut-off dates. The procedure provides two main pieces of information: the survival function—the proportion of the population ‘surviving’ a given time interval (i.e., who have not reached the terminal event), and the hazard function—the proportion of the surviving population who are likely to reach the event within the interval (i.e., risk of the terminal event occurring). Survival analysis has als