Citation

Thien, Bryan Chek Hui and Yeong, Wai Chung and Lim, Sok Li and Chong, Zhi Lin and Khoo, Michael B. C. (2025) Monitoring the Coefficient of Variation Using a Synthetic Exponentially Weighted Moving Average Chart. Quality and Reliability Engineering International. ISSN 0748-8017

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Abstract

Coefficient of variation (γ) charts are widely adopted in many industries to monitor processes without a consistent mean (μ) and which has a standard deviation (σ) that is dependent on μ. The exponentially weighted moving average (EWMA) and synthetic (Syn) γ charts show different strengths, where the EWMA γ chart is sensitive toward small and moderate shifts, while the synthetic γ chart shows better sensitivities toward large shifts. Hence, the Syn-EWMA γ chart is proposed, where it combines the features of both charts. This paper contributes to the literature by (i) developing the proposed chart's operations; (ii) deriving the formulae of the average run length (ARL), standard deviation of the run length (SDRL), and expected average run length (EARL); and (iii) formulating algorithms that optimize its performance. The proposed chart is shown to outperform the Shewhart, EWMA, and synthetic γ charts across all shifts. Lastly, the implementation on a sintering process is shown.

Item Type:	Article
Subjects:	Q Science > QA Mathematics > QA150-272.5 Algebra
Divisions:	Faculty of Computing and Informatics (FCI)
Depositing User:	Ms Suzilawati Abu Samah
Date Deposited:	05 May 2025 01:19
Last Modified:	05 May 2025 01:19
URII:	http://shdl.mmu.edu.my/id/eprint/13761

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