EFFECT OF PROCESS FAILURE MECHANISMS ON ECONOMIC (X)OVER-BAR CONTROL CHARTS

There has been considerable research on the economic design of Statist ical Process Control models, for example on xBAR charts. Much of this research has assumed either a discrete event or continuous time proces s. However, virtually no research has been reported on continuous time models which formally investigate the effects of the choice of proces s failure mechanism on its design parameters. Using a continuous time model, we show empirically that such model design parameters are affec ted by the choice of process failure mechanism. The significance of th is influence depends on the size of a process shift that one wishes to detect. The smaller the shift, the more significant the effect on the design parameters. For process shifts of 1 standard deviation or more , the design parameters are essentially robust with respect to choice of process failure mechanism.