The variable sample size and sampling interval run sum Max chart

A variable sample size and sampling interval run sum Max chart (VSSI-RSMax) is proposed to efficiently monitor the mean and/or variability of a process. The VSSI-RSMax chart varies the sample size and sampling interval of the RSMax chart according to the current cumulative score. A Markov chain method is used to evaluate the performance of the proposed chart in terms of the average time to signal (ATS), the adjusted average time to signal (AATS), and the expected AATS (EAATS). The VSSI-RSMax chart is compared with other competitive single control charts, such as the standard fixed sample size and sampling interval (FSSI) Max chart, the VSSI-Max chart, the FSSI-RSMax chart, the FSSI Max-EWMA and the FSSI Max-CUSUM. Also, the implementation of the VSSI-RSMax chart in practice is demonstrated with an illustrative example.