Modified EWMA control chart for transformed gamma data

Abstract

The current article, design a control chart using a modified exponentially weighted moving average statistic (using transformation) which further enhance the sensitivity of the EWMA chart under the assumption that the quality characteristic of interest follows the gamma distribution. The necessary measures are determined to design the proposed chart and to evaluate its performance for in-control and out-of-control situations. The performance comparison of the proposed chart in terms of average run length is made with two existing control charts. The results of the study are shown that the proposed chart is an efficient chart than its two existing competitive control charts for detecting out-of-control process quickly. The application of the proposed chart is given with the help of an industrial example.

KEYWORDS:

• Gamma distribution
• EWMA
• modified EWMA
• transformed data
• Average run length

Acknowledgments

The authors are deeply thankful to the editor and reviewers for their valuable suggestions to improve the quality of the paper.