A nonparametric control chart based on the Mood statistic for dispersion: Control chart based on the Mood statistic

摘要

Control charts are used as a statistical process control (SPC) to distinct the presence of an assignable cause of variation in the process. The advantage of the nonparametric control charts is that the nonparametric charts can be useful in statistical process control problems when there is a lack of knowledge about the underlying process distribution. In this paper, the nonparametric control chart is considered based on the rank sum statistic for dispersion. In the case of small sample sizes, the exact control limits are derived. For the large sample sizes, the control limits are evaluated by using the normal and saddlepoint approximations. The nonparametric charting statistic is applied for the real data.