BAYESIAN S AND S~2 CONTROL CHARTS FOR PROCESS VARIATION

摘要

Process variability has an important role in the process of manufacturing. Shewhart's standard deviation (SD) chart (S chart) is first of its kind for process variability. In this paper, we construct SD(S) and variance (S2) posterior control charts for process variation using Bayesian approach. We assume that the prior distribution of the process variance is a mixture of several (k known) inverted gamma distributions. The control limits of S chart, probability limits of both S and S2 charts are derived. The charts are evaluated in terms of their width, power and Average Run Length (ARL).