A study on the median run length performance of the run sum S control chart

Control charts play a very important role in Statistical Process Control. Run sum S control chart is sensitive in detecting small to moderate shifts. It is an excellent alternative to Shewhart control chart. The performance of the run sum S control chart based on median run length (MRL) performance is proposed in this study. The Statistical Analysis System (SAS) program was used to calculate the in-control ARL and in-control MRL for the nine run sum S chart schemes with different sample sizes, magnitude of shift in the process standard deviation, and the in-control run lengths. The findings show that the MRL measure provides better explanation than the ARL criterion. Moreover, the MRL performance of the run sum S chart schemes is substantially affected by the sample sizes, magnitude of shift in the process standard deviation, and the in-control run lengths.