標題: Assessing the actual Gamma process quality - a curve-fitting approach for modifying the non-normal flexible index
作者: Liao, Mou-Yuan
Pearn, W. L.
Liu, Yen-Lun
工業工程與管理學系
Department of Industrial Engineering and Management
關鍵字: curve fitting;flexible capability index;Gamma distribution;non-normal
公開日期: 3-Aug-2015
摘要: Process capability indices (PCIs) have been widely adopted for quality assurance activities. By analysing PCIs, a production department can trace and improve a poor process to enhance product quality level and satisfy customer requirements. Among these indices, C-pk remains the most prevalent for facilitating managerial decisions because it can provide bounds on the process yield for normally distributed processes. However, processes are often non-normal in practice, and C-pk may quite likely misrepresent the actual product quality. Hence, the flexible index C-jkp, which considers possible differences in the variability above and below the target value, has been developed for practical use. However, C-jkp continues to suffer from serious bias in assessing actual capability, especially when the process distribution is highly skewed. In this paper, we modify C-jkp for assessing the actual process quality of a Gamma process. A correction factor is obtained by the curve-fitting method. The results show that our proposed method can significantly reduce the bias for calculation of actual nonconformities. Moreover, we introduce a sample estimator for our modified index. The ratio of this estimator\'s average value and the modified index is approximately 1. This implies that our proposed estimator can provide an appropriate estimation for assessing the actual Gamma process quality.
URI: http://dx.doi.org/10.1080/00207543.2015.1041572
http://hdl.handle.net/11536/127839
ISSN: 0020-7543
DOI: 10.1080/00207543.2015.1041572
期刊: INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH
Volume: 53
Issue: 15
起始頁: 4720
結束頁: 4734
Appears in Collections:Articles