Lower confidence limits of process capability indices for non‐normal process distributions
International Journal of Quality & Reliability Management
ISSN: 0265-671X
Article publication date: 1 December 1998
Abstract
When the process probability distribution is non‐normal or is unknown, the process mean and standard deviation may not properly describe the distribution’s shape. Consequently, the traditional process capability indices (PCI) Cp, Cpk, Cpm and Cpmk cannot express the actual process capability. This paper presents a procedure to construct lower confidence limits for PCIs when the process distribution is unknown. First, the order statistics are utilized to find the estimators of Cp, Cpk, Cpm and Cpmk. Bootstrap simulation method is then utilized to construct the lower confidence limits of PCIs, thereby allowing the process’s capability to be evaluated. A numerical example demonstrates the effectiveness of the proposed procedure.
Keywords
Citation
Tong, L. and Chen, J. (1998), "Lower confidence limits of process capability indices for non‐normal process distributions", International Journal of Quality & Reliability Management, Vol. 15 No. 8/9, pp. 907-919. https://doi.org/10.1108/02656719810199006
Publisher
:MCB UP Ltd
Copyright © 1998, MCB UP Limited