| Summary: | 碩士 === 國立交通大學 === 工業工程與管理學系 === 100 === Process capability indices (PCIs) for processes with a single quality characteristic have been investigated extensively. For processes involved multiple characteristics, we consider the one-sided process capability index CpuT. However, the exact sampling distribution of CpuT is mathematically intractable. In this research, in order to make inferences on the process capability, we apply an asymptotic normal distribution for the natural estimator of CpuT and investigate the accuracy with the corresponding sample size by simulation. In addition, depending on the sample size, a performance comparison among the normal approximate method and four kinds of the bootstrap approach for 95% lower confidence bounds is conducted based on coverage rate and mean of the lower confidence bounds. Finally, an application from manufacturing process with multiple characteristics is presented. In general, the result indicates that the normal approximate technique is more reliable than the four bootstrap methods.
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