A control chart for the coefficient of variation

Chang W. Kang, Man S. Lee, Young J. Seong, Douglas M. Hawkins

Research output: Contribution to journalArticlepeer-review

93 Scopus citations

Abstract

Monitoring variability is a vital part of modern statistical process control. The conventional Shewhart R and S charts address the setting where the in-control process readings have a constant variance. In some settings, however, it is the coefficient of variation, rather than the variance, that should be constant. For example, this setting is common in clinical chemistry, and then conventional R and S charts cannot be used. This paper develops a chart, equivalent to the S chart, for monitoring the coefficient of variation using rational groups of observations.

Original languageEnglish (US)
Pages (from-to)151-158
Number of pages8
JournalJournal of Quality Technology
Volume39
Issue number2
DOIs
StatePublished - Jan 1 2007

Keywords

  • Clinical chemistry
  • Process variability
  • Statistical process control

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