2000 Volume 51 Issue 5 Pages 409-415
Assume that the quality characteristics obey a normal distribution. Recently, Kanagawa et al. (1993) proposed a (x^^-, s) simultaneous control chart based on the estimator of Kullback-Leibler information. Further, based on the results derived by Arizono et al. (1995), we can evaluate the power characteristics for out-of-control state using the simultaneous control chart. Then, the (x^^-, s) simultaneous control chart is designed to conform with the probability limit method and enables the user to monitor both changes in mean and variance simultaneously. By the way, Daudin (1992) proposed a double-sampling x^^- control chart, which is the counterpart to double-sampling plans. However, in a physical environment, it is usual to jointly employ the x^^- chart for monitoring the shift in process mean and the R chart for monitoring the change in process variance. Then, the application of the double-sampling procedure to the x^^--R chart is somewhat complicated as many design parameters and compound judgements are required. On the other hand, the (x^^-, s) simultaneous control chart for monitoring both changes in mean and variance simultaneously has less design parameters and simple judgement in comparison with the x^^--R control chart. In this paper, the double-sampling procedure is applied to the (x^^-, s) simultaneous control chart, then a double-sampling (x^^-, s) simultaneous control chart is proposed. Furthermore, the performance of the double-sampling (x^^-, s) simultaneous control chart is compared with the performance of the standard (x^^-, s) simultaneous control chart.
