Phase II exponential charts for monitoring time between events data: performance analysis using exact conditional average time to signal distribution

In this paper, we study the performance properties of phase II exponential chart with an unknown in-control (IC) rate parameter, used to monitor high-yield processes. The average time signal (ATS) is as criterion instead usual run length (ARL). Based on IC conditional ATS (CATS) distribution, examine both equal-tailed and ATS-unbiased charts estimated control limits adjust so that a nominal achieved. Two perspectives are investigated: unconditional, under which CATS distribution set equal and, or exceed high probability. It shown perspective has better performance.