ECONOMIC DESIGN OF (X)OVER-BAR CONTROL CHARTS ASSUMING WEIBULL IN-CONTROL TIMES

A computer program is presented that determines the economically optim al design parameters for (X) over bar control charts where the amount of time the process remains in control has a Weibull distribution. Res ults of both uniform and non-uniform inspection schemes are presented. For a uniform inspection scheme, the lengths of the sampling interval s are constant. For a non-uniform inspection scheme, however, the leng ths of the sampling intervals are chosen to maintain a constant integr ated hazard rate over each sampling interval. A single assignable caus e model is assumed. The optimal values of the design parameters, sampl e size, sampling intervals, and control limit coefficient are determin ed by minimizing the expected cost per unit time.