An adaptive run sum scheme for process ratio

Tracking the ratio of two normal variables (RTNV) is crucial in ensuring the quality regarding some manufacturing processes. In this study, the run sum and variable sampling interval procedures are combined to develop a more effective scheme for controlling the RTNV A comparison with the existing basic ratio and run sum ratio schemes, as per average time to signal criterion, shows that the new chart substantially surpasses its two existing counterparts. An example of application using factual data is given to showcase the operation of the new scheme in practice.