Improving Shewhart control chart performance for monitoring the Weibull mean

• Published in: Quality and reliability engineering international Vol. 37; no. 3; pp. 984 - 996
• Main Authors: Ho, Linda Lee, Fernandes, Fidel Henrique, Quinino, Roberto C., Bourguignon, Marcelo
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01-04-2021
• Subjects: average run length; Control charts; Monitoring; Performance enhancement; probability control limits; simplified variable sample sizes; simulation; Weibull distribution
• ISSN: 0748-8017; 1099-1638
• DOI: 10.1002/qre.2777

In this paper, we are interested in monitoring the stability of a Weibull process mean. We introduce a simplified variable sample size (SVSS) procedure, which consists of using alternately sample sizes nA and nB with nA>nB, to improve the performance of the traditional X¯ control chart (a fixed sample size n). Operationally, the proposal is relatively simple and its adoption yields a faster signal of an abnormal situation compared with the traditional X¯ chart in a variety of shifts. We present instructions for practitioners on how to design a control chart using the SVSS procedure. We also illustrate the proposed scheme through a numerical example.