Comparison study of different control charts for joint monitoring of mean and variance

Abstract

Control charts are used for the purpose of detecting assignable causes. It is standard practice to use an $\overline{X}$ chart for detecting assignable causes that shift the process mean, and an R-chart for detecting assignable causes shift in the process variability. The joint use of $\overline{X}$ and R charts has been extensively studied for monitoring processes for searching assignable causes that shifts the process mean and increases variability. In the recent past researchers are working on one chart which serves the purpose of  joint monitoring scheme for controlling process mean and variance simultaneously. Between the various joint monitoring charts, it is important to know which one is better than others. For that a comparison study is required. The main purpose of this work is to compare between three important joint monitoring charts viz.  NCS control chart, Max control chart and MSE control chart and study their efficiency to detect the shift in mean and variance simultaneously.