A side-sensitive synthetic chart combined with a VSS X¯ chart

Abstract

In independent investigations, the variable sample size (VSS) scheme and the side-sensitive synthetic (SS) rule proved to reduce the delay with which the X¯ chart signals. Based on these findings we investigate the X¯ chart's performance with the joint use of the VSS scheme and the side-sensitive synthetic rule. The SSVSS X¯ chart outperforms the pure VSS X¯ chart, especially when the risk of false alarms and the rate of inspected items per sampling cannot be high. In these cases, the VSS X¯ chart detects moderate mean shifts (around one standard deviation) in half of the time thanks to the side-sensitive synthetic rule.