In statistical process control (SPC), t charts play a vital role in the monitoring of the process mean, especially when the process variance is unknown. In this paper, two separate upper-sided and lower-sided exponentially weighted moving average (EWMA) t charts are first proposed and the Monte Carlo simulation method is used to obtain their run length (RL) properties. Compared with the traditional one-sided EWMA t charts and several run rules t charts, the proposed charts are proven to have better performance than these competing charts. In addition, by adding the variable sampling interval (VSI) feature to the proposed charts, the new VSI one-sided EWMA t charts are shown to detect different shift sizes in the process more efficient than the chart without VSI feature. Finally, an example of a milk filling process illustrates the use of the charts.

中文翻译：

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带有和不带有可变采样间隔的新单面EWMA t图表，用于监视过程平均值

在统计过程控制（SPC）中，t图在过程均值的监视中起着至关重要的作用，尤其是在过程方差未知的情况下。在本文中，首先提出了两个单独的上侧和下侧指数加权移动平均值（EWMA）t图，并使用蒙特卡罗模拟方法获得了它们的行程长度（RL）属性。与传统的单面EWMA t图表和多个运行规则t图表相比，事实证明，与其他竞争图表相比，所提出的图表具有更好的性能。此外，通过在建议的图表中添加可变采样间隔（VSI）功能，新的VSI单面EWMA t图中显示的图表比没有VSI功能的图表更有效地检测过程中的不同班次大小。最后，以牛奶填充过程为例说明了图表的使用。