針對製程產品的變異數，文獻上大多是監控變異數增加的部份，而忽略了變異數減少時所帶來的訊息，當製程的變異數變小時，則代表製程的改善，這時候就應該要重新設定管制圖，才能做有效的製程監控。我們將文獻上已存在的監控變異數變大的管制圖推廣到監控變異數變小以及同時監控變異數增加或減少的情形，另外，我們也提出兩種新的管制圖來與文獻上的管制圖做比較，並觀察製程在發生階梯式平移及漂移式失控時，四種管制圖的失控狀態平均連串長度的大小。此外，在變異數雙邊的監控方面，我們將監控變異數增加較有效率的管制圖與監控變異數減少較有效率的管制圖合併，合併後的管制圖能有效的監控變異數的雙邊改變。最後我們討論文獻上所提出的最佳化設計，我們建議使用此種最佳化設計前，需要先定義平滑常數的範圍，才能使之更實用。

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