A Study on Evaluation of Stability in Process Mean Using Bayesian Updating

It is common that a manufacturing process is unstable at the beginning of operation. Then, a process condition is brought into being stable with the lapse of time. The evaluation of stability is very important to process management in order to shift to mass production. In this study, we propose a method of evaluating the stability in a process. In a detail, we investigate a conjugate distribution of the process mean based on Bayesian theory first. In particular, we consider the difference between both of the prior and posterior probability distributions in the process mean to be a criterion for the stability of a process. Hence, we evaluate the difference between the both distributions using information theory. Then, a numerical example in the method of evaluating the stability in a process is shown.