Variance estimation of a survival function for interval-censored survival data

Interval-censored survival data often occur in medical studies, especially in clinical trials. In this case, many authors have considered estimation o f a survival function. There is, however, relatively little discussion on e stimating the variance of estimated survival functions. For right-censored data, a special case of interval-censored data, the most commonly used meth od for variance estimation is to use the Greenwood formula. In this paper w e propose a generalization of the Greenwood formula for variance estimation of a survival function based on interval-censored data. Also a simple boot strap approach is presented. The two methods are evaluated and compared usi ng simulation studies and a real data set. The simulation results suggest t hat the methods work well. Copyright (C) 2001 John Wiley & Sons, Ltd.