Browsing by Author "Shu, M. H."

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Bootstrap approach for supplier selection based on production yield
(2008)
Wu, C. -W.
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Shu, M. H.
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Pearn, W. L.
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Liu, K. H.
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工業工程與管理學系
Current manufacturing industries have increased their level of out-sourcing and relied more heavily on their supply chain as a source of competitive advantage. Supplier selection decisions have become an important component of production management. Those decisions have a significant impact on a firm's marketing competition, and suppliers may account for a large portion of the production cost. Production quality is one of the key factors in supplier evaluation. The manual of supplier certification includes a discussion of process capability analysis, which recommends a procedure for evaluating the most prevalent process capability index Cpk. However, the recommended procedure is applicable only when evaluating an individual supplier's performance. In this paper, we apply the bootstrap method to the supplier selection problem. We construct lower confidence intervals for the capability difference and ratio between two given suppliers. Performance comparisons are made among various bootstrap methods in terms of error probability and selection power. For convenience of applications, the sample sizes required for various designated selection power are also tabulated.
Measuring process capability based on Cpmk with gauge measurement errors
(2007-08-01)
Hsu, B. M.
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Shu, M. H.
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Pearn, W. L.
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工業工程與管理學系
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Department of Industrial Engineering and Management
Due to their effectiveness and simplicity of use, the process capability indices Cp, Cpk, and Cp. have been popularly accepted in the manufacturing industry as management tools for evaluating and improving process quality. Combining the merits of those indices, a more advanced index, C(pmk), is proposed that takes into account process variation, process centering, and the proximity to the target value, and has been shown to be a very useful index for manufacturing processes with two-sided specification limits. Most research works related to Cpmk assume no gauge measurement errors. However, such an assumption inadequately reflects real situations even when highly advanced measurement instruments are employed. Conclusions drawn regarding process capability are therefore unreliable and misleading. In this paper, we conduct a sensitivity investigation for the process capability index Cpmk in the presence of gauge measurement errors. We consider the use of capability testing Of C(pmk) as a method for obtaining lower confidence bounds and critical values for true process capability when gauge measurement errors are unavoidable. The results show that using the estimator with sample data contaminated by measurement errors severely underestimates the true capability, resulting in an imperceptibly smaller test power. To measure the true process capability, three methods for the adjusted confidence bounds are presented and their performances are compared using computer simulation. Copyright (C) 2006 John Wiley & Sons, Ltd.