Monitoring high-quality processes with one-sided conditional cumulative counts of conforming chart

Abstract

Due to the development of high-quality manufacturing processes, a cumulative count of conforming (CCC) chart has been demonstrated to be useful in high-quality manufacturing processes for monitoring the nonconforming fraction. When the quality characteristic is asymmetric and the one-directional shifting is of interest, a one-sided control chart is more appropriate than a two-sided chart. We construct a one-sided CCC chart for high-quality processes based on previous runs to improve its sensitivity. The results show that the proposed conditional procedure method of the one-sided CCC chart can detect the shift quickly when the process begins to deteriorate at the beginning. A real case example of medication error is illustrated using the proposed charting technique. It shows that the proposed method is more suitable than traditional p-chart. The proposed conditional one-sided CCC procedure is useful in manufacturing that involves high-quality processes.