Modified Group Runs Control Charts to Detect Increases in Fraction Non Conforming and Shifts in the Process Mean

ABSTRACT

In this article, we propose ‘Modified Group Run' (MGR) charts useful to identify increases in fraction non conforming and to detect shifts in the process mean. It is verified that the MGR charts significantly reduces out of control ‘Average Time to Signal’ (ATS) as compared to most of the well-known control charts. The attribute control charts considered for comparison are the Run Length CUSUM chart (Bourke, 1991), Bernoulli CUSUM chart (Reynolds and Stoumbos, 1999), synthetic chart (Wu et al., 2001), and GR chart (Gadre and Rattihalli, 2004b). The variable control charts considered for comparison are chart, synthetic chart and GR chart (Gadre and Rattihalli, 2004a).

Keywords:

• Average Time to Signal (ATS)
• Bernoulli CUSUM chart
• CRL chart
• EWMA chart
• np Chart
• Run Length CUSUM chart
• Steady State ATS
• Synthetic chart
• X¯ chart

Mathematics Subject Classification:

• 62P30

Acknowledgments

The first author is grateful to the UGC New Delhi for awarding the Teacher fellowship to complete his research work. Both authors are grateful to the referees for their valuable suggestions, comments, and pointing out an algebraic typo, which helped to improve the manuscript significantly.