在工業統計上，產品品質的度量方法有很多，例如製程能力指標(Process Capability Indices)、故障率(Hazard Rates)及平均剩餘壽命(Mean Residual Life)等。通常產品之二維品質，都有二種表示方式，也因此有二種估計方式，本文主要目的在比較此二種估計方法之優劣。

In the industrial statistics , there are many measurable ways(example: Process Capability indices、Hazard Rates、Mean Residual Life、etc…) in quality control.
In generality , product have two reports in the two-dimensional quality. Thus , they have two estimable ways. In this paper , we will compare fit and unfit in this two estimable ways.

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