Yeong Wai  Chung, Michael Khoo Boon  Chong, Lim Sok  Li, Teoh Wei  Lin, Ng Peh  Sang, 
    Effects of Misspecification on the Economic-Statistical Design of the Coefficient of Variation Chart,
    Journal of Engineering and Applied Sciences,
    Volume 11,Issue 7,
    2016,
    Pages 1655-1659,
    ISSN 1816-949x,
    jeasci.2016.1655.1659,
    (https://makhillpublications.co/view-article.php?doi=jeasci.2016.1655.1659)
    Abstract: The Coefficient of Variation (CV) chart monitors changes in the ratio of the standard deviation against the mean, instead of monitoring changes in the mean and/or standard deviation. The economic-statistical design of the CV chart allows practitioners to select optimal chart parameters which minimize the cost subject to constraints in the run length. However, a large number of parameters need to be estimated. This study looks at the effects when these parameters are incorrectly estimated. It was found that a minimal increase in cost is shown when the parameters are not estimated accurately, except for the incorrect specification of the shift size and the out-of-control quality cost which shows a slightly higher increase in cost. Thus, only a rough approximation is needed for most of the parameters.
    Keywords: Coefficient of variation chart;economic-statistical design;incorrect specification;increase in cost;rough approximation