Reliable confidence intervals for assessing normal process incapability

ABSTRACT

This study aims to provide a reliable confidence interval for assessing the process incapability index [C_pp]. The concept of the generalized pivotal quantities is utilized for constructing the generalized confidence interval for [C_pp]. And, simulations are performed for demonstrating our proposed method and one existent method. The results show that the empirical confidences of these two methods are significantly affected by the degree of process departure. Therefore, we suggest the practitioners to select proper one for capability testing purpose based on the information of degree of process departure.

Keywords:

• Generalized confidence intervals
• Process incapability
• Quality assurance

Mathematics Subject Classification:

• 62 Statistics
• 90-08 Computational methods

Acknowledgment

The authors would like to express their gratitude to the Editor Narayanaswamy Balakrishnan and the anonymous referees for their helpful comments and suggestions that significantly improved the presentation of this article.

Funding

This research was partially supported by the National Science Council of Taiwan under Grant No. NSC 101-2410-H-126-035. The authors would like to appreciate the grant for this research.