Atta, Abdu. M. A., and Razamin Ramli. 2011. “A Comparison Study on the Performances Of X , EWMA and CUSUM Control Charts for Skewed Distributions Using Weighted Standard Deviations Methods”. Journal of Science and Technology 3 (2). https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/358.