The article proposes a Shewhart-type control chart, namely Mt chart, for an improved monitoring of the mean level of a quality characteristic of interest, say Y, in a process. The proposed control chart uses the information on a single auxiliary characteristic, say X, of the process and is based on product–difference-type estimator, say Mt (in fact the spirit is to pool different styles of using information on auxiliary variable(s)). Assuming bivariate normality of the characteristic of interest Y and the auxiliary characteristic X, design structure of the proposed Mt chart is developed and its comparisons are made with those of some existing control charts used for the same purposes. The comparisons reveal an improved performance of the proposed Mt chart relative to its existing counterparts due to suggested merger of different approaches.
