比例型態隨機變數的估計與推論常應用於不同的統計問題上,例如: 線性模式之反預測, 邊際藥劑量, 相關效力等問題;在衰退測試實驗中，線性衰退路徑的隨機效果亦構成此種型態之隨機變數.伯恩斯坦式是建立於描述切割工具壽命而產生的,已被工程界廣泛運用於描述元件壽命.我們以傳統的估計方法, %calibration華德統計量和最大概似比檢定對比例型態問題推論與估計,並和伯恩斯坦模式相比較.當衰退模式中斜率項為正之假設不成立時,Hinkley (1969) 所整理二項常態比例之分配,提供了一個精確的分配形態.在伯恩斯坦模式中,線性衰退路徑之截距與斜率推廣至二項分配之形態,並進一步討論其他分配型態的截距與斜率之情況.

　　The inference of ratio-typed random variables occurred often in different application situations,for example calibration, critical dosage,relative potency, etc. Estimation of failure time distribution in linear degradation model with random intercept and slope also involves ratio of two random variables. Bernstein model has been established in degradation analysis in estimating a time-to-failure distribution. In this work, we study the approaches of Wald and maximum likelihood, compared with Bernstein distribution, in estimation and making inference of ratio-typed quantity of interest. Profile likelihood is used to construct confidence interval in likelihood approach.The distribution of the ratio of bivariate normally distributed random variables is discussed by Hinkley (1969),it provides an exact and correct distribution of Bernstein model when the assumption of positive slope is not hold.

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