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Monitoring the Coefficient of Variation Using a Variable Sampling Interval Control Chart
Author(s) -
Castagliola Philippe,
Achouri Ali,
Taleb Hassen,
Celano Giovanni,
Psarakis Stelios
Publication year - 2013
Publication title -
quality and reliability engineering international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 62
eISSN - 1099-1638
pISSN - 0748-8017
DOI - 10.1002/qre.1465
Subject(s) - control chart , statistics , \bar x and r chart , shewhart individuals control chart , x bar chart , ewma chart , statistical process control , chart , coefficient of variation , sampling (signal processing) , mathematics , interval (graph theory) , control limits , computer science , process (computing) , filter (signal processing) , combinatorics , computer vision , operating system
The coefficient of variation (CV) is a quality characteristic that has several applications in applied statistics and is receiving increasing attention in quality control. Few papers have proposed control charts that monitor this normalized measure of dispersion. In this paper, an adaptive Shewhart control chart implementing a variable sampling interval (VSI) strategy is proposed to monitor the CV. Tables are provided for the statistical properties of the VSI CV chart, and a comparison is performed with a Fixed Sampling Rate Shewhart chart for the CV. An example illustrates the use of these charts on real data gathered from a casting process. Copyright © 2012 John Wiley & Sons, Ltd.