Designing of a hybrid exponentially weighted moving average control chart using repetitive sampling

Abstract

A hybrid exponentially weighted moving average (HEWMA) control chart using repetitive sampling is presented in this manuscript. The designing of the proposed control chart is developed for a normally distributed quality characteristic. The formulas for the in-control and the out-of-control average run lengths (ARLs) are derived. Control chart coefficients are determined by considering the target in-control ARL. The tables for ARLs are presented for various target in-control ARLs and process shift parameters. The performance of the proposed control chart is compared with the existing control chart in terms of ARLs, which shows that the proposed chart performs better in detecting relatively small process mean shifts. An industrial example is given for the illustration purpose.