SHEWHART AND ZONE CONTROL CHART PERFORMANCE UNDER LINEAR TREND

ABSTRACT

The average run length performances of Shewhart charts with supplementary runs rules and zone control charts are studied when the process mean changes linearly over time. Shewhart charts with all possible combinations of the typical runs rules are compared to zone control charts with identical false alarm rates. The zone control charts generally outperform the Shewhart charts in detecting a process mean that is changing linearly over time.

Keywords:

• Control charts
• Average run length
• Shewhart chart
• Zone control chart
• Linear trend

ACKNOWLEDGMENTS

The authors wish to thank the referees, whose suggestions improved the presentation of this material.