Process capability control chart for non-normal data – evidence of on-going capability assessment

Abstract

Process capability indices are widely used for various quality assurance activities in many high-tech industries. By a suitable analysis of an index, a production department can trace and improve a poor process to enhance the quality level and satisfy customer requirements. Recently, some practical process capability control charts were developed for illustrating the continuous assessments of normal process capability. These charts contain information regarding the ability of the process to meet or exceed customer requirement over the life of a process. Monitoring the behaviour of the process’s ability to meet customer requirement can provide managers with feedback and evidence of the process’s ability in terms they understand. However, process distribution is often ab normal. Therefore, this study incorporates bootstrap procedure to construct capability control chart for non-normal processes. The simulations show that the empirical coverage probability of this chart is close to the desired coverage probability as the number of subgroup is large enough.

Keywords:

• Bootstrap
• non-normal
• process capability

Disclosure statement

This research was partially supported by the National Science Council of Taiwan under Grant No. NSC 99-2410-H-264-008. The author would like to appreciate the grant for this research.

Notes on contributor

Mou-Yuan Liao, is currently an Associate Professor in the Department of Statistics and Informatics Science at Providence University, Taiwan. He received his MS degree from the Institute of Statistics at Cheng Kung University, Taiwan, and PhD degree in Industrial Engineering and Management from the National Chiao Tung University, Taiwan. His research interests include statistical process control, production management, and statistical computing.