An application of confirmation sample control chart in the high-yield processes and its economic design

This paper presents a modified CS(Confirmation Sample) chart for detecting sensitively small or moderate changes in p for both of upward and downward shifts in high-yield processes. The simplified design of the modified CS chart is done by applying the design method of the CS chart for the Shewhart-type charts to the CCC(Cumulative Count of Conforming)-r chart dealing with the cumulative count of items inspected until observing r nonconforming items. As r gets larger, the modified CS chart, named the CS(CCC-r) chart, becomes more and more sensitive to small or moderate changes in p for both of upward and downward shifts, but the CS(CCC-r) chart needs more and more observations to obtain a plotting point on the CS(CCC-r) chart, so the cost is fairly high. In this paper, a simplified optimal economic design method for the CS(CCC-r) chart is also proposed. For illustrative purposes, some numerical results for the optimal design parameter values are provided.