Bridging the gap between theory and practice in basic statistical process monitoring

ABSTRACT

Some issues are discussed relative to the gap between theory and practice in the area of statistical process monitoring (SPM). Among other issues, it is argued that the collection and use of baseline data in Phase I needs a greater emphasis. Also, the use of sample ranges in practice to estimate process standard deviations deserves reconsideration. A discussion is given on the role of modeling in SPM. Then some work on profile monitoring and the effect of estimation error on Phase II chart performance is summarized. Finally, some ways that researchers could influence practice more effectively are discussed along with how SPM research could become more useful to practitioners.

KEYWORDS:

• average run length
• control chart
• false alarm rate
• SPC
• SPM
• statistical process control

About the author

William H. Woodall is a Professor in the Department of Statistics at Virginia Tech. He is a former editor of the Journal of Quality Technology (2001–2003) and associate editor of Technometrics (1987–1995). He is the recipient of the Box Medal (2012), Shewhart Medal (2002), Jack Youden Prize (1995, 2003), and Brumbaugh Award (2000, 2006). He is a Fellow of the American Statistical Association, a Fellow of the American Society for Quality, and an elected member of the International Statistical Institute.

Acknowledgments

The author appreciates the helpful comments from a number of Virginia Tech graduate students and Willis Jensen of W. L. Gore.

Funding

The author's work was supported in part by National Science Foundation Grant CMMI-1436365.