Asymmetric control limits of the x ‐bar chart for skewed process distributions

Presents an approach to determine the optimum control limits of the x ‐bar chart for skewed process distributions. The approach takes both the control limits of the x ‐bar chart and the specification limits of x into consideration, and relates the out‐of‐control status directly with the nonconforming products. The proposed approach may be applied to industries to reduce the average number of scrap products, without increasing the type I error in statistical process control (SPC).