A robust alternative to Hotelling's T2 control chlart using trimmed estimators

A control chart is one of the primary techniques used in statistical process control. In phase 1, historical observations are analysed in order to construct a control chart with which to determine whether the process has been in control over the period of time in which the data were collected. The presence of multiple outliers may go undetected by the usual control charts, such as Hotelling's T-2 due to the masking effect. In this paper we propose a robust alternative to Hotelling's T-2 control chart with estimators defined using trimming. Simulation studies show that the proposed control chart is more effective than T-2 in detecting outliers. Copyright (C) 2008 John Wiley & Sons, Ltd.