A new method for obtaining the TTT plot for a censored sample

For a censored sample where withdrawns or suspensions are present, Kaplan-Meier-estimation (KME) method, also called product-limit-estimation (PLE) method, and piecewise-exponential-estimation (PEXE) method, have been typically used to estimate both the survivor function (or cdf) and the total time on test (TTT) statistic at each observed failure time. This paper presents a new method, called mean-order-number (MON) method, for estimating TTT statistics and TTT plot for a censored sample. This method is illustrated using Dodson's example as quoted by numerous authors. A comparison is made among MON, KME, and PEXE. It turns out that MON method is not only easy to use but its results are consistent with KME and PEXE as well.