Comparison of single EWMA-type control charts based on Economic- statistical design
نویسندگان
چکیده
Abstract A single exponentially weighted moving average (EWMA) chart is effectively used for monitoring the process mean and variance simultaneously. In this paper, three single EWMA-type control charts including sum of square EWMA (SS-EWMA), maximum EWMA (MaxEWMA), and EWMA-semicircle (EWMA-SC) charts are compared under Lorenzen and Vance’s cost model integrating Taguchi’s loss function. The optimal decision variables, namely sample size n , sampling interval time h , control limit width L , and smoothing constant , are obtained by minimizing the expected cost function. Via simulations, the EWMA-SC charts have the smallest expected cost among these charts when a process has large shifts. However, the MaxEWMA charts have the smallest expected cost among these charts when a process mean shifts.
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