Control Charts for Joint Monitoring of the Lognormal Mean and Standard Deviation

The Shewhart X¯- and S-charts are most commonly used for monitoring the process mean variability based on assumption of normality. However, many distributions may follow a positively skewed distribution, such as lognormal distribution. In this study, we discuss construction three combined jointly standard deviation. simulation results show that more effective when distribution is skewed. A real example to demonstrate how can be applied in practice.