Search

A lower-sided and an upper-sided exponentially weighted moving average (EWMA) chart for detecting mean changes (decreases and increases) in processes characterized by Weibull distributions are developed in this paper when censoring occurs at a fixed level. We show that the lower-sided EWMA chart performs better than its counterpart, the Shewhart-type; that a Shewhart-type chart is not appropriate to detect mean increases when the censoring rate is high; and that the upper-sided EWMA chart works well in detecting mean increases. [ABSTRACT FROM AUTHOR]

Proposes a chart for an improved monitoring of the p fraction. Two alternatives to the p chart; Guidelines for choosing an appropriate chart; Advantages of simple adjustments; Explanation of T.P. Ryan's rule of thumb.