A Group Runs Control Chart for Detecting Shifts in the Process Mean

Wu and Spedding [Journal of Quality Technology 32: 32-38, 2000] have proposed the synthetic control chart to detect small shifts in process mean. In this paper, for the same problem, we propose a control chart called ’Group Runs’ (GR) control chart, which is a combination of Shewhart's chart and an extended version of conforming run length chart. It is numerically verified that, the GR chart gives a significant reduction in out of control ATS as compared to those of the synthetic control chart and chart when in-control ATS is not smaller than a certain number. Steady state performance of the GR chart is also better. Hence, GR chart turns out to be economical to detect small shifts in the process mean.