Non-normality and combined double sampling and variable sampling interval [image omitted] control charts

A combination of double sampling the [image omitted]  chart and the variable sampling interval of the [image omitted]  chart (DSVSI [image omitted]  chart) increases the sensitivity in the small shift detection. A usual assumption of control charts is that the process observations are normally distributed. However, this assumption may not be true for some processes in the real industry. This paper presented the performance of DSVSI [image omitted]  chart under non-normality and compared it with the Shewhart [image omitted]  chart and the variable parameters [image omitted]  chart. The compared results show that the DSVSI [image omitted]  chart has the best performance in detecting small process mean shifts.