Robustness of Group Runs Control Chart to Non-normality

Most of the commonly used control charts for variables have been developed under the assumption that the observations are coming from a normal population. One of them is ‘Group Runs’ GR control chart to detect shifts in the process mean proposed by Gadre and Rattihalli (Economic Quality Control 19: 29–43, 2004). In this article, we study the robustness of GR chart to violation of the assumption of normality. It is observed that, for moderate to large shifts in the process mean, GR chart is insensitive to the non-normality. It is also illustrated that, the GR chart performs better than the synthetic chart, when the process data are not coming from normal distribution.