THE DESIGN OF ACCEPTANCE CONTROL CHART FOR NON-NORMAL DATA

Abstract

ABSTRACT Control charts often are designed under the normality assumption. But in some manufacturing processes this assumption may not be valid. Tsai [12] developed a skew normal X control chart to monitor the process average for non-normal data. He showed that a considerable improvement over those of existing control charts can be achieved when the skew normal X control chart is used to monitor the process average. Based on the skew normal X control chart, the paper develops a skew normal acceptance control chart to monitor the process average and the fraction of nonconformities for non-normal data. The proposed acceptance control chart reduces to the conventional acceptance control chart as the underlying distribution of measurements is symmetric. Two examples are given for illustration. The presented examples show that the construction of the proposed acceptance control chart is easy, moreover, ignoring the non-normality effect will result in a higher type I or type II error probability.