Estimating sigma and Improving Control Limits with RWAV for Normal and Non-normal Processes

摘要

In this article, we compare the statistical properties of R, S, and RWAV methods for estimation of variance of a process for quality control purposes. We investigate effects of non-normality for different estimators. Our results indicate that RWAV gives the best estimates of the standard deviations for both normal and non-normal processes. We recommend the construction of control charts with RWAV.