Monitoring the Process Mean and Variance Using Individual Observations and Variable Sampling Intervals
Monitoring the Process Mean and Variance Using Individual Observations and Variable Sampling Intervals
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DOI：
10.1080/00224065.2001.11980066
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发表时间：
2001-04
影响因子：
2.5
通讯作者：
M. R. Reynolds;Z. G. Stoumbos
中科院分区：
文献类型：
--
作者：
M. R. Reynolds;Z. G. Stoumbos
在本文中，我们研究控制图的监测过程中检测的平均值和/或方差的正常质量变量时，在每个采样点采取的个人观察的变化。对传统的X图和移动极差图进行了评价。还评估了观测值的指数加权移动平均（EWMA）图和观测值与目标的平方偏差的EWMA图。它示出的X和MR图的组合将不会检测到小的和中等的参数变化一样快的组合，涉及EWMA图。图表的能力来诊断的类型的参数偏移产生的一个特殊的原因也进行了研究。它表明，涉及EWMA图的组合是一样有效的诊断类型的参数偏移的X和MR图的传统组合。还评估了添加可变采样间隔（VSI）功能对某些图表组合的影响。VSI功能允许采样间隔根据所绘制的统计值而变化。结果表明，添加VSI功能的组合图表的结果在非常大的减少所需的预期时间来检测过程参数的变化。
In this paper we investigate control charts for monitoring a process to detect changes in the mean and/or variance of a normal quality variable when an individual observation is taken at each sampling point. The traditional X chart and moving range (MR) chart are evaluated. Also evaluated are the exponentially weighted moving average (EWMA) chart of the observations and the EWMA chart of the squared deviations of the observations from the target. It is shown that the combination of the X and MR charts will not detect small and moderate parameter shifts as fast as combinations involving the EWMA charts. The ability of charts to diagnose the type of parameter shift produced by a special cause is also investigated. It is shown that combinations involving the EWMA charts are just as effective at diagnosing the type of parameter shift as the traditional combination of the X and MR charts. The effect of adding the variable sampling interval (VSI) feature is also evaluated for some of the combinations of charts. The VSI feature allows the sampling interval to be varied as a function of the values of the statistics being plotted. It is shown that adding the VSI feature to the combinations of charts results in very substantial reductions in the expected time required to detect shifts in process parameters.