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The Global ETD Search service is a free service for researchers
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Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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雙變量脆弱性韋伯迴歸模式之研究余立德, Yu, Li-Ta Unknown Date (has links)
摘要
本文主要考慮群集樣本(clustered samples)的存活分析，而每一群集中又分為兩種組別(groups)。假定同群集同組別內的個體共享相同但不可觀測的隨機脆弱性(frailty)，因此面臨的是雙變量脆弱性變數的多變量存活資料。首先，驗證雙變量脆弱性對雙變量對數存活時間及雙變量存活時間之相關係數所造成的影響。接著，假定雙變量脆弱性服從雙變量對數常態分配，條件存活時間模式為韋伯迴歸模式，我們利用EM法則，推導出雙變量脆弱性之多變量存活模式中母數的估計方法。
關鍵詞：雙變量脆弱性，Weibull迴歸模式，對數常態分配，EM法則 / Abstract
Consider survival analysis for clustered samples, where each cluster contains two groups. Assume that individuals within the same cluster and the same group share a common but unobservable random frailty. Hence, the focus of this work is on bivariate frailty model in analysis of multivariate survival data. First, we derive expressions for the correlation between the two survival times to show how the bivariate frailty affects these correlation coefficients. Then, the bivariate log-normal distribution is used to model the bivariate frailty. We modified EM algorithm to estimate the parameters for the Weibull regression model with bivariate log-normal frailty.
Key words：bivariate frailty, Weibull regression model, log-normal distribution, EM algorithm.
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漲跌停板限制下之股票報酬機率分配葉宜欣, Yeh, Yi-Shian Unknown Date (has links)
股票市場的報酬率相對於金融市埸是非常重要的，因為其背後的真實機率分配對各種資產定價及選擇權的評價模型都有決定性的影響。本文考慮台灣股票市埸具有漲跌停板的限制來驗證實證中股票報酬機率分配的「厚尾」的現象，希望透過我們的研究能對財務理論在國內金融市埸的應用有更進一步的了解。我們選定了常態分配、對數常態分配及一般化第二種貝它分配 (GB2)來當作是台灣股票報酬率的真實機率分配，以動差法比較再以概似比檢定法(LR test)選出一表現最好的機率分配。由選取的25支國內股票中發現一般化第二種貝它分配 (GB2)可以解釋偏態和峰態對報酬率的影響並且也是概似比檢定法所選出的最適報酬率分配，由此可知一般化第二種貝它分配 (GB2)較為適合作為台灣股票報酬的真實機率分配。
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