The impact of estimated parameters to the double sampling and variable sampling interval X chart

The DSVSI X̅ char has been explored extensively by many researchers because its strong ability to detect small and moderate mean shifts. Most researchers are investigating under the assumption of known process parameters. In practice, process parameters are rarely unknown and they need to be estimated from an in-control historical Phase-I dataset. Therefore, in this paper we consider the estimated parameters, by calculate the ATS to evaluate the performance of the DSVSI char when process parameters are estimated and is compared with the case where process parameters are known.