一种改进的中位数图

One Improved Sample Median Chart

基于Klein的x-控制图模型提出一种改进的中位数图.此图的失控条件是两个连续样本中位数均落在上警戒域或均落在下警戒域或有一个样本中位数落在行动域.采用马氏链方法计算了此图的平均链长.与标准休哈特x~图进行了比较,显示此x图在保持对大漂移发现速度的同时,能更快的发现过程均值小的漂移.

This paper proposed an improved median chart based on Klein model of x control chart. The out-of-control condition was that both of two successive sample medians fell in the upper warning zone or in the lower warning zone or any sample median fell beyond a control limit. A Markov chain method was used to compute the average run length. The comparison with the Shewhart x showed that this chart was superior in performance for small process average drift, while maintaining the same sensitivity in the detection of large drift.