Robust X̄ control chart for monitoring the skewed and contaminated process

Abstract

In this paper, we propose the modified Shewhart, the modified weighted variance and the modified skewness correction methods by using trimmed mean and interquartile range estimators to construct the control limits of robust X̄ control chart for monitoring the skewed and contaminated process. A comparison between the performances of the X̄ chart for monitoring the process mean based on these three modified models is made in terms of the Type I risk probabilities and the average run length values for the various levels of skewness as well as different contamination models.