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Full-Text Articles in Physical Sciences and Mathematics

Racial Disparities Study In Diabetes-Related Complication Using National Health Survey Data, Fengxia Yan Dec 2010

Racial Disparities Study In Diabetes-Related Complication Using National Health Survey Data, Fengxia Yan

Mathematics Theses

The main aim of this study is to compare the prevalence of diabetes-related complications in white to the prevalence in other racial and ethnic groups in United States using 2009 Behavioral Risk Factor Surveillance System (BRFSS). By constructing the logistic regression model, odds ratios (OR) were calculated to compare the prevalence of diabetes complications in white and other groups. Compared to white, the prevalence of hypertension and stroke in African Americans were higher, while the prevalence of heart attack and coronary heart disease were lower. The Asian Americans or Pacific Islanders, African Americans and Hispanics were more likely to develop …


Empirical Likelihood Confidence Intervals For Roc Curves Under Right Censorship, Hanfang Yang Sep 2010

Empirical Likelihood Confidence Intervals For Roc Curves Under Right Censorship, Hanfang Yang

Mathematics Theses

In this thesis, we apply smoothed empirical likelihood method to investigate confidence intervals for the receiver operating characteristic (ROC) curve with right censoring. As a particular application of comparison of distributions from two populations, the ROC curve is constructed by the combination of cumulative distribution function and quantile function. Under mild conditions, the smoothed empirical likelihood ratio converges to chi-square distribution, which is the well-known Wilks's theorem. Furthermore, the performances of the empirical likelihood method are also illustrated by simulation studies in terms of coverage probability and average length of confidence intervals. Finally, a primary biliary cirrhosis data is used …


Looking In The Crystal Ball: Determinants Of Excess Return, Kokou S. Akolly Aug 2010

Looking In The Crystal Ball: Determinants Of Excess Return, Kokou S. Akolly

Mathematics Theses

This paper investigates the determinants of excess returns using dividend yields as a proxy in a cross-sectional setting. First, we find that types of industry and the current business cycle are determining factors of returns. Second, our results suggest that dividend yield serves a signaling mechanism indicating “healthiness” of a firm among prospective investors. Third we see that there is a positive relationship between dividend yield and risk, especially in the utility and financial sectors. And finally, using actual excess returns, instead of dividend yield in our model shows that all predictors of dividend yield were also significant predictors of …


Cox Model Analysis With The Dependently Left Truncated Data, Ji Li Aug 2010

Cox Model Analysis With The Dependently Left Truncated Data, Ji Li

Mathematics Theses

A truncated sample consists of realizations of a pair of random variables (L, T) subject to the constraint that L ≤T. The major study interest with a truncated sample is to find the marginal distributions of L and T. Many studies have been done with the assumption that L and T are independent. We introduce a new way to specify a Cox model for a truncated sample, assuming that the truncation time is a predictor of T, and this causes the dependence between L and T. We develop an algorithm to obtain the adjusted risk sets and use the Kaplan-Meier …


Weak Primary Decomposition Of Modules Over A Commutative Ring, Harrison Stalvey Apr 2010

Weak Primary Decomposition Of Modules Over A Commutative Ring, Harrison Stalvey

Mathematics Theses

This paper presents the theory of weak primary decomposition of modules over a commutative ring. A generalization of the classic well-known theory of primary decomposition, weak primary decomposition is a consequence of the notions of weakly associated prime ideals and nearly nilpotent elements, which were introduced by N. Bourbaki. We begin by discussing basic facts about classic primary decomposition. Then we prove the results on weak primary decomposition, which are parallel to the classic case. Lastly, we define and generalize the Compatibility property of primary decomposition.