ITS ABOUT TIME - USING DISCRETE-TIME SURVIVAL ANALYSIS TO STUDY DURATION AND THE TIMING OF EVENTS

Educational researchers frequently ask whether and, if so, when events occur. Until relatively recently, however, sound statistical methods for answering such questions have not been readily available. In this article, by empirical example and mathematical argument, we demonstrat e how the methods of discrete-time survival analysis provide education al statisticians with an ideal framework for studying event occurrence . Using longitudinal data on the career paths of 3,941 special educato rs as a springboard, we derive maximum likelihood estimators for the p arameters of a discrete-time hazard model, and we show how the model c an be fit using standard logistic regression software. We then disting uish among the several types of main effects and interactions that can be included as predictors in the model, offering data analytic advice for the practitioner. To aid educational statisticians interested in conducting discrete-time survival analysis, we provide illustrative co mputer code (SAS, 1989) for fitting discrete-time hazard models and fo r recapturing fitted hazard and survival functions.