This project will investigate theory, methods and applications of mathematical statistics and probability, with particular emphasis on the problems with data collected by NICHD. Current focus is on 1) the analysis of data arising from longitudinal studies with repeated measurements, 2)nonparametric procedures, 3) likelihood approaches to nonparametric two-sample problem for right-censored data, 4) sequential clincial trials, and 5) general methodology for reproductive and perinatal epidemiology. Examples of NICHD projects on longitudinal studies are Successive Small-for-Gestational Age Study I and Study II in Alabama and Scandinavia, and the Longitudinal Study of Vaginal Flora. A host of statistical procedures for estimation and hypothesis testing will be proposed and investigated for the time varying coefficient models via their asymptotic properties and simulations. Applications will be developed to handle questions concerning various issues in perinatal and reproductive epidemiology. New and rigorous statistical methods and algorithms will be generated and validated through investigation of their statistical and probabilistic properties. Computer-intensive techniques such as bootstrapping methodology will be investigated for the relevant problems. Among the applications of the developed methodology are fetal growth, maternal risk factors and pregnancy outcomes. Regression models for unbalanced longitudinal ordinal data will be studied. Major motivation and application come from the Longitudinal Study of Vaginal Flora. One direction is to develop sequential methodologies for clinical trials. Particular focus will be on the estimation problems following the termination of a clinical trial. Adaptive designs in clinical trials will be studied. Also under investigation is the incorporation of partial overrruning into the final analysis of a sequential clinical trial. Longitudinal analysis for discrete data and sequential adaptive designs will be the major focus for the near future. Point and interval estimation for two-stage adaptive procedures will be studied. A two-stage adaptive procdeure will be designed for the selection of the best diagnostic biomarker.

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Vexler, Albert; Wu, Chengqing; Yu, Kai Fun (2010) Optimal Hypothesis Testing: From Semi to Fully Bayes Factors. Metrika 71:125-138
Wu, Mi-Xia; Yu, Kai-Fun; Liu, Ai-Yi (2009) Estimation of Variance Components in the Mixed-Effects Models: A Comparison Between Analysis of Variance and Spectral Decomposition. J Stat Plan Inference 139:3962-3973
Zhang, Jun; Villar, Jose; Sun, Wenyu et al. (2007) Blood pressure dynamics during pregnancy and spontaneous preterm birth. Am J Obstet Gynecol 197:162.e1-6
Levine, Richard J; Lam, Chun; Qian, Cong et al. (2006) Soluble endoglin and other circulating antiangiogenic factors in preeclampsia. N Engl J Med 355:992-1005
Levine, Richard J; Qian, Cong; Maynard, Sharon E et al. (2006) Serum sFlt1 concentration during preeclampsia and mid trimester blood pressure in healthy nulliparous women. Am J Obstet Gynecol 194:1034-41
Signore, Caroline; Mills, James L; Qian, Cong et al. (2006) Circulating angiogenic factors and placental abruption. Obstet Gynecol 108:338-44
Troendle, James F; Liu, Aiyi; Wu, Chengqing et al. (2005) Sequential testing for efficacy in clinical trials with non-transient effects. Stat Med 24:3239-50
Liu, Aiyi; Wu, Chengqing; Yu, Kai F et al. (2005) Supplementary analysis of probabilities at the termination of a group sequential phase II trial. Stat Med 24:1009-27
Levine, Richard J; Qian, Cong; Leshane, Erik S et al. (2004) Two-stage elevation of cell-free fetal DNA in maternal sera before onset of preeclampsia. Am J Obstet Gynecol 190:707-13
Klebanoff, Mark A; Schwebke, Jane R; Zhang, Jun et al. (2004) Vulvovaginal symptoms in women with bacterial vaginosis. Obstet Gynecol 104:267-72

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