AN ALTERNATIVE DESIGN FOR THE VARIABLE SAMPLE SIZE COEFFICIENT OF VARIATION CHART BASED ON THE MEDIAN RUN LENGTH AND EXPECTED MEDIAN RUN LENGTH

Authors

  • Sok Li Lim Universiti Malaya
  • Wai Chung Yeong Sunway University
  • Michael Boon Chong Khoo Universiti Sains Malaysia
  • Zhi Lin Chong Universiti Tunku Abdul Rahman
  • Khai Wah Khaw Universiti Sains Malaysia

DOI:

https://doi.org/10.23055/ijietap.2019.26.2.4085

Keywords:

coefficient of variation, expected median run length, median run length, percentiles of the run length distribution, variable sample size

Abstract

Control charts for monitoring the coefficient of variation (CV) are attracting increasing attention in recent years. These charts are able to monitor processes with an unstable mean and/or standard deviation, but has a stable CV. Existing CV charts are designed based on the average run length (ARL) criterion. However, this paper has shown that designs based on the ARL criterion could result in misinterpretation of the chart’s actual performance. Hence, this paper proposes alternative designs for the VSS CV chart, based on the median run length (MRL) and expected median run length (EMRL) criteria. This paper also compares the performance of the VSS CV chart with that of the Exponentially Weighted Moving Average (EWMA) and Shewhart CV charts, based on the proposed designs. Subsequently, this paper shows the implementation of the proposed designs on an industrial example. 

Published

2019-06-26

How to Cite

Lim, S. L., Yeong, W. C., Khoo, M. B. C., Chong, Z. L., & Khaw, K. W. (2019). AN ALTERNATIVE DESIGN FOR THE VARIABLE SAMPLE SIZE COEFFICIENT OF VARIATION CHART BASED ON THE MEDIAN RUN LENGTH AND EXPECTED MEDIAN RUN LENGTH. International Journal of Industrial Engineering: Theory, Applications and Practice, 26(2). https://doi.org/10.23055/ijietap.2019.26.2.4085

Issue

Section

Quality, Reliability, Maintenance Engineering