A combined adaptive double sampling and variable sampling interval control chart for monitoring three-level products

Abstract

Three-level control charts have been developed for monitoring processes where the quality of products is characterized by classifying the product characteristic into three discrete levels. In this article, a combined double sampling and variable sampling interval (DSVSI) attribute control chart is developed for monitoring three-level products. This research is motivated by recent studies done on combining the DSVSI scheme with traditional attribute charts and their results recommend the application of the DSVSI attribute charts. The proposed DSVSI three-level chart is compared with the existing standard, adaptive, and EWMA three-level charts. The results approve the superiority of the proposed scheme and recommend it as an efficient three-level control chart in application. An example is also provided to illustrate the application of the proposed chart.

KEYWORDS:

• Three-level control chart
• double sampling
• variable sampling interval
• quality value function
• adjusted average time to signal

Acknowledgments

The Authors wish to acknowledge the helpful suggestions of the Editor-in-Chief, gratefully acknowledging the valuable suggestions and comments of two reviewers, guided to revise an improvement version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The financial supports of Natural Science and Engineering Research Council (NSERC) of Canada are also gratefully acknowledged.