本研究針對兩個相依製程下兩個等級產品之製程管制提出以統計方法管制製程和以經濟觀點管制製程。在統計製程管制方面，本研究在製程的第一階段建立個別等級的EWMA管制圖和合併的EWMA管制圖以快速地偵測出影響個別等級產品品質特性之非機遇因素是否發生及同時影響所有等級產品品質特性之非機遇因素是否發生；在第二階段建立個別等級的選控圖和合併的選控圖以快速地偵測出影響個別等級產品品質特性之非機遇因素是否發生及同時影響所有等級產品品質特性之非機遇因素是否發生。利用這些管制圖不但考慮到前後製程的關係，在製程失控時更可明確地劃分各個子製程的責任歸屬。本研究並以資料分析比較EWMA管制圖和選控圖、Shewhart Individual管制圖與Hotelling 管制圖的診斷效果。在經濟設計方面，本研究發展經濟設計的EWMA管制圖和選控圖以分別監控生產兩個等級產品之兩階段製程。文中將製程表示為更新過程，而更新過程中每一個循環又被表示為馬可夫過程，於是利用馬可夫鏈方法及更新過程性質可導出成本函數。由於導出的單位時間成本是管制圖設計參數的函數，故用最佳解技巧即可決定設計參數的最佳值。文中並以數值分析與例子說明經濟設計的EWMA管制圖和選控圖的設立及應用。

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