THE GENERALLY WEIGHTED MOVING AVERAGE CONTROL CHART FOR DETECTING SMALL SHIFTS IN THE PROCESS MEDIAN

摘要

This study proposes the generally weighted moving average (GWMA) control chart for monitoring the process sample median. The GWMA control chart is a generalization of the EWMA control chart. The properties and design strategies of the GWMA median control chart are investigated. We use simulation to evaluate the average run length properties of the EWMA median control chart and the GWMA median control chart. After an extensive comparison, it reveals that the GWMA median control chart performs much better than the EWMA median control chart for detecting small shifts in the process sample median. An example is given to illustrate this study.