中文摘要：

传统的EWMA控制图分别针对监控过程均值变化和监控过程标准差变化进行研究,在实际生产中,很多情形需要同时监控过程均值变化和过程标准差变化。为了提高控制图的监控效率,本文研究了同时监控均值和标准差变化时,EWMA控制图的可变抽样区间设计。其次运用马科夫链法计算可变抽样区间EWMA控制图的平均报警时间;然后与传统的EWMA控制图进行比较得出：同时监控均值和标准差时,可变抽样区间的EWMA控制图能够更快地发现过程中的异常波动,具有较短的平均报警时间,其监控效率明显优于传统的EWMA控制图。

英文摘要：

The traditional EWMA control charts for monitoring the process mean or process standard deviation changes were investigated respectively.In actual production,the process mean and standard deviation should be monitored at the same time for a lot of circumstances.In order to improve the monitoring efficiency of control charts,the EWMA control chart for monitoring process mean and standard deviation with variable sampling intervals（VSI）is constructed in this paper.The Markov chain method is applied to calculate the average time to signal（ATS）of the VSI EWMA control charts.The computing results show that the VSI EWMA control chart for monitoring process mean and standard deviation is the more efficient in detecting shifts than the traditional EWMA control chart,and has the shorten average time to signal to find the abnormal fluctuation.