Feedback adjustment using exponentially weighted moving average schemes

Abstract

In this study, we discuss the use of exponentially weighted moving average (EWMA) schemes in feedback adjustment for process improvement. By application the different measures of dispersion yield different optimal values. In particular it is suggested that a robust statistic based on the median is more appropriate than the usual mean of square error (MSE).We also consider an autoregressive time series model for modeling the deviations from target and this model is compared with the usual EWMA model. The problem of applying feedback adjustment to a controllable process is discussed and it is shown via a simulation that correlation structure of the data of interest play a critical role on whether the MSE after adjustment is lower than the MSE before adjustment.