One-Sided Shewhart-type Charts for Monitoring the Coefficient of Variation in Short Production Runs

Abstract

Monitoring the coefficient of variation is an effective approach to Statistical Process Control when the process mean and standard deviation are not constant but their ratio is constant. Until now, research has not investigated the monitoring of the coefficient of variation for short production runs. Viewed under this perspective, this paper proposes a new method to monitor the coefficient of variation for a finite horizon production by means of one-sided Shewhart-type charts. Tables are provided for the statistical properties of the proposed charts when the shift size is deterministic. Two illustrative examples are given in order to illustrate the use of these charts on real data.

Key Words:

• Coefficient of variation
• shewhart-type chart
• short production runs
• truncated run length.

Additional information

Notes on contributors

Philippe Castagliola

Philippe Castagliola is graduated (Ph.D. 1991) from the UTC (Universite de Technologie de Compiegne, France). He is currently professor at the Universite de Nantes, Institut Universitaire de Technologie de Nantes, France, and he is also a member of the IRCCyN (Institut de Recherche en Communications et Cybernetique de Nantes), UMR CNRS 6597. He is associate editor for the International Journal of Reliability, Quality and Safety Engineering. His research activity includes developments of new SPC techniques (non normal control charts, optimized EWMA type control charts, control charts with estimated parameters, multivariate capability indices, monitoring of batch processes, …).

Asma Amdouni

Asma Amdouni is graduated from the Universite de Tunis, Institut Superieur de Gestion, Tunisie. She is currently a Ph.D. student at the Universite de Nantes and at the Universite de Tunis. She is a member of the IRCCyN (Institut de Recherche en Communications et Cybernetique de Nantes), and LAROdEc (Laboratoire de Recherche Operationnelle, de Decision et de Controle de Processus). His thesis research is focused on Control Chart Specification using Coefficient of Variation in Short Production Runs.

Hassen Taleb

Hassen Taleb is graduated (Ph.D. 2006) from the university of Tunis, Tunisia. He is currently associate professor at the University of Gafsa, and he is also the Director of the “Institut Superieur d‘Administration des Entreprises” de Gafsa, Tunisia. He is also a member of the LARODEC (Laboratory of Operational Research, Decision Making and Process Control. His research activity includes SPC developments and applications (control charts for multinomial processes, fuzzy control charts, self-starting control chart, dOe, …).

Giovanni Celano

Giovanni Celano has a Master Degree in Mechanical Engineering and holds a Ph.D. in Manufacturing Engineering from the University of Palermo (Italy). Currently, he is assistant professor at the University of Catania (Italy), where he teaches Quality Management. His research is mainly focused on Statistical Quality Control. He is currently Associate Editor of the Quality Technology and Quantitative Management journal and the Journal of Industrial Engineering. He is member of the Associazione Italiana di Tecnologia Meccanica (AITeM) and the European Network of Business and Industrial Statistics (ENBIS).