Improved simultaneous monitoring of mean and coefficient of variation under ranked set sampling schemes

Abstract

A control chart is very useful to control assignable causes that detect the shifted process parameters (e.g., mean and dispersion). Simultaneous monitoring of the process parameters is a well-known approach utilized for the bilateral processes. This paper explores the joint monitoring to study the impact of both process mean and coefficient of variation (CV) by using log-normal transformation under ranked set sampling (RSS) schemes. Utilizing RSS schemes in joint monitoring of mean and CV with exponentially weighted moving average (EWMA) statistic enhances the capacity of the monitoring plan as compare to EWMA with simple random sampling for a mean shift, CV shift as well as joint shift. RSS schemes using EWMA can lessen the antagonistic impact on recognizing the capacity of a joint monitoring plan. The illustration of the proposed control chart is presented with the aid of a real data set.

Keywords:

• Control chart
• CV
• EWMA
• Joint monitoring
• RSS

MATHEMATICAL SUBJECT CLASSIFICATION:

• 62P30

Acknowledgments

The authors are grateful to the reviewers for their suggestions which helped in improving substantially, the earlier version of this article.