Rejoinder

Kaplan–Meier graphs of survival and other timed events are an extremely effective way to summarize outcome data from some types of clinical studies, but information on dates and the interaction among events is lost. A new mode for presenting such data is proposed, an Eventchart, that aids in looking at the study as a whole by simultaneously displaying the timing of 2–3 different types of events, including censoring and time-dependent covariate events. The chart helps to monitor accrual and can be used to “guesstimate” the amount of information resulting from additional enrollment and/or follow-up. Eventcharts are designed to supplement, not replace, quantitative methods of analysis or conventional survival graphs. Data from bone marrow transplantation and AIDS studies are used to illustrate the method. Terminology is suggested for describing the concepts and distinguishing among the complex of events studied in modern clinical trials, including timed events, loss and date censoring, and time-braided events.     

Rejoinder

Abstract

In this article several formulae for the approximation of the critical values for tests on the actual values of the process capability indices CPL, CPU, and C_pk are provided. These formulae are based on different approximations of the percentiles of the noncentral t distribution and their performance is evaluated by comparing the values assessed through them from the exact critical values, for several significance levels, test values, and sample sizes. As supported by the obtained results, some of the presented techniques constitute valuable tools in situations where the exact critical values of the tests are not available, since one may approximate them readily and rather accurately through them.