Statistics Seminar - Control Charts for Coefficient of Variation

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TITLE: Control Charts for Coefficient of Variation

SPEAKER: Dr. Chang W. Kang


In some manufacturing processes, the variance can change, depending on the process mean. For example, if the output value reflects process yield, an increased mean might naturally lead to an increase in variance. When the variance is a function of the mean, the coefficient of variation (CV) is an appropriate measure for process variability. Since the CV control chart was first introduced by Kang et al (2007), there were some trials to improve the performance of CV control charts depending on the shift size.

In this research, we present some CV related control charts and compare the performance of those control charts for better use in the field. The CV control chart shows good sensitivity to large shift in CV. The CV-EWMA control chart(2008), the CV-DEWMA control chart(2011) and the CV-GWMA control chart(2011) were developed to control processes sensitively responding to small shifts of CV. The FIR CV-GWMA control chart is more effective control chart to detecting off-target processes in the stage of set-up or start-up of process.

Host: Professor Paul Kvam <>




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