Monitoring General Linear Profiles When Random Errors Have Contaminated Normal Distributions

We consider the quality of a process which can be characterized by a general linear profile where the random error has a contaminated normal distribution. On the basis of trimmed least squares estimation, new control charts for monitoring the coefficient parameters and/or the error variance of the profile are proposed. Simulation studies show that the proposed control charts outperform the existing competitors under such a profile. An example from manufacturing facility is used to illustrate the applicability of the proposed charts.