IMPLEMENTING STATISTICALLY CONSTRAINED ECONOMIC EWMA CONTROL CHARTS

A computer program is presented for the statistically constrained economic design of exponentially weighted moving average control charts for controlling process means. The program finds the optimal sample size, control limit width, sampling interval, and weighting factor by minimizing a total cost function proposed by Lorenzen and Vance subject to additional statistical constraints on average run length (ARL) or average time-to-signal (ATS). The ARL values are determined by solving systems of linear algebraic equations using Gaussian quadrature, following the integration-equation approach outlined by Crowder.