The DS control chart was firstly proposed by Croasdale [5] in control charts for variables. In this first DS control chart, information from the first and second samples is evaluated separately, and confirmation is done only with the second sample. Daudin [6] improved Croasdale’s DS control chart, and proposed a DS control chart that uses the information from both samples at the second stage. The larger sample size improves the precision of the control chart since it uses a smaller sample standard deviation. In estimating the control chart limits, Daudin’s DS control chart is optimized with respect to the expected sample size. Instead of minimizing the expected sample size, [8] maximized the power of the control chart to determine the control chart limits. He et al. [7] and Costa and Claro [4] have made further development of DS control chart for variables.