EWMA(Exponentially Weighted Moving Average)管制圖(control chart)在統計製程管制(statistical process control)上是目前最好的檢測方法，但是當誤差量小的時候，其效率並沒有很好。本文利用逐次概率比檢定(Sequential Probability Ratio Test)的最佳性質，將所有觀測值透過函數轉換以及累加所得，作為檢定統計量，當此統計量超出一設定界線時判定為製程失控(out of control)。期望此方法在小的誤差量中會比EWMA管制圖表現地更好，透過模擬及比較後，發現此方法在小的誤差量中確實會比EWMA管制圖有效率，而且效率是非常顯著的。本文最後討論轉換函數的參數值該如何選取，使得皆可適用於各種不同的情況。

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