Robust X¯ Control Chart for Monitoring the Skewed and Contaminated Process

Abstract

In this paper, we propose the modi fied Shewhart, the modifi ed weighted variance and the modifi ed skewness correction methods by using trimmed mean and interquartile range estimators to construct the control limits of robust $\bar{X}$ control chart for monitoring the skewed and contaminated process. A comparison between the performances of the $\bar{X}$ chart for monitoring the process mean based on these three modi fied 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.