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 highyield 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.