Title: "Control Charts with Estimated Parameters"

Speaker: Philippe Castagliola, University of Nantes

Date:26 January 2012

Time:13:00-14:00

Room:607, 6th floor, Evelpidon building

AbstractWhen monitoring a process using control charts, it is a common practice that a Phase I data set is used to estimate both the unknown in-control process mean ì

_{0}and the in-control process standard-deviation ó_{0}. Once the process is considered to be in-control, these estimated control limits are assumed as fixed. This common practice totally ignores the effect of estimating ì_{0}and ó_{0}and the strong impact in terms of Run Length properties (pdf, cdf, ARL, SDRL,...). In this presentation, we will focus on two S^{2}type control charts (Shewhart, EWMA) with estimated parameters. We will also demonstrate that the Run Length properties of these charts are different when the parameters are known and when they are estimated and we will suggest new control chart parameters which depend on the number m of Phase I samples. As an alternative, we will investigate the t and EWMA t charts that do not require any Phase I estimation for ó_{0}.