Monitoring process mean level using auxiliary information

In this study, a Shewhart-type control chart is proposed for the improved monitoring of process mean level (targeting both moderate and large shifts which is the major concern of Shewhart-type control charts) of a quality characteristic of interest Y. The proposed control chart, namely the M-r chart, is based on the regression estimator of mean using a single auxiliary variable X. Assuming bivariate normality of (Y, X), the design structure of M-r chart is developed for phase I quality control. The comparison of the proposed chart is made with some existing control charts used for the same purpose. Using power curves as a performance measure, better performance of the proposed M-r chart is observed for detecting the shifts in mean level of the characteristic of interest.