Statistics and Probability Commons^™

Mediation Analysis With Time-Varying Exposures And Mediators, Tyler J. Vanderweele, Eric Tchetgen Tchetgen

Harvard University Biostatistics Working Paper Series

In this paper we consider mediation analysis when exposures and mediators vary over time. We give non-parametric identification results, discuss parametric implementation, and also provide a weighting approach to direct and indirect effects based on combining the results of two marginal structural models. We also discuss how our results give rise to a causal interpretation of the effect estimates produced from longitudinal structural equation models. When there are no time-varying confounders affected by prior exposure and mediator values, identification of direct and indirect effects is achieved by a longitudinal version of Pearl's mediation formula. When there are time-varying confounders affected …

Comparing Partial Least Square Approaches In Gene-Or Region-Based Association Study For Multiple Quantitative Phenotypes, Zhongshang Yuan, Xiaoshuai Zhang, Fangyu Li, Jinghua Zhao, Fuzhong Xue

Human Biology Open Access Pre-Prints

On thinking quantitatively of complex diseases, there are at least three statistical strategies for association study: single SNP on single trait, gene-or region (with multiple SNPs) on single trait and on multiple traits. The third of which is the most general in dissecting the genetic mechanism underlying complex diseases underpinning multiple quantitative traits. Gene-or region association methods based on partial least square (PLS) approaches have been shown to have apparent power advantage. However, few attempts are developed for multiple quantitative phenotypes or traits underlying a condition or disease, and the performance of various PLS approaches used in association study for …

Global Resource Management Of Response Surface Methodology, Michael Chad Miller

Dissertations and Theses

Statistical research can be more difficult to plan than other kinds of projects, since the research must adapt as knowledge is gained. This dissertation establishes a formal language and methodology for designing experimental research strategies with limited resources. It is a mathematically rigorous extension of a sequential and adaptive form of statistical research called response surface methodology. It uses sponsor-given information, conditions, and resource constraints to decompose an overall project into individual stages. At each stage, a "parent" decision-maker determines what design of experimentation to do for its stage of research, and adapts to the feedback from that research's potential …

Qualitative Behavior Of Solutions Of Difference Equations With Several Oscillating Coefficients, Martin Bohner, George E. Chatzarakis, Ioannis P. Stavroulakis

Mathematics and Statistics Faculty Research & Creative Works

Sufficient conditions which guarantee the convergence of the non-oscillatory solutions or oscillation of all solutions of a difference equation with several deviating arguments and oscillating coefficients are presented. Corresponding difference equations of both retarded and advanced type are studied. Examples illustrating the results are also given. [Media Object not available: see full text.]

Clinical Trials And Late-Stage Drug Development In Alzheimer’S Disease: An Appraisal From 1984 To 2014, L. S. Schneider, F. Mangialasche, S. Andreasen, H. Feldman, E. Giacobini, R. Jones, V. Mantua, P. Mecocci, L. Pani, B. Winblad, M. Kivipelto

Human Clinical Trials Collection

The modern era of drug development for Alzheimer's disease began with the proposal of the cholinergic hypothesis of memory impairment and the 1984 research criteria for Alzheimer's disease. Since then, despite the evaluation of numerous potential treatments in clinical trials, only four cholinesterase inhibitors and memantine have shown sufficient safety and efficacy to allow marketing approval at an international level. Although this is probably because the other drugs tested were ineffective, inadequate clinical development methods have also been blamed for the failures. Here, we review the development of treatments for Alzheimer's disease during the past 30 years, considering the drugs, …

Media Portrayal Of Individuals In The Lower Class And Its Effects On Attributions Of Educational Hardships, Krista A. Burke

Communication Studies

This study investigated how media portrayals of individuals in the lower class affect people’s beliefs about educational hardships in lower socioeconomic areas. Specifically, this study looked at the attributions of these hardships to determine if media consumption had an effect on the internality of attributions. It was hypothesized that increased media consumption would be related to an increased tendency toward internal attributions. It was hypothesized that increased media consumption would lead to lower support for policy changes regarding education. A survey was distributed to assess media consumption habits and attitudes toward educational hardships in the lower class. Correlation results yielded …

Mobilizing Mechanically Ventilated Neuroscience Patients - A Clinical Practice Guideline To ‘Get Up And Go’, Bonnie Wasilowsky Bspa-Hca, Rn, Cnrn

Patient Care Services / Nursing

No abstract provided.

Benefits And Barriers To Hiv Testing In A Population Of Federal Detention Inmates, Nicole A. Knight

Loma Linda University Electronic Theses, Dissertations & Projects

Voluntary HIV testing in combination with early medical intervention has been shown to be effective in reducing the rate of new infections and improving the health and life expectancy of those living with HIV. There are however several high-risk populations in the US that remain largely unreached by HIV testing efforts, some of which could be reached while they spend time in prison or jail. Per current Bureau of Prisons (BOP) policy, HIV testing is routinely offered only to “high risk” pretrial and sentenced inmates. We conducted a cross-sectional study with 721 pretrial and sentenced inmates who entered a large …

Determining California National Guard Airmen’S Opinions And Attitudes Regarding Morale, Welfare And Recreation Programs: A Research Project, Natalie Delossa

Journalism

This senior project creates research design parameters that will facilitate two- way communications between the California Air National Guard and its airmen. The benefits of conducting its research are twofold. First, the California Air National Guard can learn more about its airmen. Second, the California Air National Guard can use information about its airmen to better serve its external publics in future public relations and marketing endeavors.

This project addresses the importance of conducting two- way communication between internal and external publics (in this case, the California Air National Guard and its airmen and the California Air National Guard and …

Mcdonald Log-Logistic Distribution With An Application To Breast Cancer Data, M. H. Tahir, Muhammad Mansoor, Muhammad Zubair, Gholamhossein Hamedani

Mathematics, Statistics and Computer Science Faculty Research and Publications

We introduce a five-parameter continuous model, called the McDonald log-logistic distribution, to extend the two-parameter log-logistic distribution. Some structural properties of this new distribution such as reliability measures and entropies are obtained. The model parameters are estimated by the method of maximum likelihood using L-BFGS-B algorithm. A useful characterization of the distribution is proposed which does not require explicit closed form of the cumulative distribution function and also connects the probability density function with a solution of a first order differential equation. An application of the new model to real data set shows that it can give consistently better fit …

A Phylogenetic Model For Understanding The Effect Of Gene Duplication On Cancer Progression, Qin Ma, Jaxk H. Reeves, David A. Liberles, Lili Yu, Zheng Chang, Jing Zhao, Juan Cui, Ying Xu, Liang Liu

Biostatistics: Faculty Publications

As biotechnology advances rapidly, a tremendous amount of cancer genetic data has become available, providing an unprecedented opportunity for understanding the genetic mechanisms of cancer. To understand the effects of duplications and deletions on cancer progression, two genomes (normal and tumor) were sequenced from each of five stomach cancer patients in different stages (I, II, III and IV). We developed a phylogenetic model for analyzing stomach cancer data. The model assumes that duplication and deletion occur in accordance with a continuous time Markov Chain along the branches of a phylogenetic tree attached with five extended branches leading to the tumor …

The Art Of Personal Science, Jeff Fajans

The Transdisciplinary STEAM+ Journal

Quantified Self isn’t really about finding answers or solving problems—it’s about asking new questions.

Regression Modeling Of Longitudinal Binary Outcomes With Outcome-Dependent Observation Times, Kay See Tan, Andrea B. Troxel, Stephen E. Kimmel, Kevin G. Volpp, Benjamin French

UPenn Biostatistics Working Papers

Conventional longitudinal data analysis methods assume that outcomes are independent of the data-collection schedule. However, the independence assumption may be violated, for example, when adverse events trigger additional physician visits in between prescheduled follow-ups. Observation times may therefore be associated with outcome values, which may introduce bias when estimating the eect of covariates on outcomes using standard longitudinal regression methods. Existing semi-parametric methods that accommodate outcome-dependent observation times are limited to the analysis of continuous outcomes. We develop new methods for the analysis of binary outcomes, while retaining the exibility of semi-parametric models. Our methods are based on counting process …

Utility Of Recommendation Letters And Correlation With Specific Residency Applicant Qualities, Joseph E. Patruno Md, Amanda B. Flicker Md, Craig Koller Med, Amy B. Smith Phd, Hubert K. Huang Ms, Med, Taylor N. Weilnau

Department of Obstetrics & Gynecology

No abstract provided.

Gender Differences In Perceptions And Self-Reported Driving Behaviors Among Teenagers. (Poster), Gavin C. Barr Jr. Md, Kathleen E. Kane Md, Robert D. Barraco Md, Timarie Rayburg Do, Lauren Dugan Do, Chadd K. Kraus Do, Mph, Marna R. Greenberg Do, Mph, Facep, Valerie Rupp Rn, Bsn, Kimberly Hamilton, Bryan G. Kane Md

Department of Emergency Medicine

No abstract provided.

A Statewide Survey Of Institutional Trauma Human Resource Allocation And Associated Patient Mortality, Bryan G. Kane Md, Quincy Gerrald Do, Catherine Fischer Do, Kevin Vong Do, Mary Sibley Do, Justin Binstead Do

Department of Emergency Medicine

No abstract provided.

Does Destination Determine Destiny? A Statewide Analysis Of Trauma Center Mortality, Bryan G. Kane Md, Quincy Gerrald Do, Catherine Fischer Do, Kevin Vong Do, Mary Sibley Do, Justin Binstead Do

Department of Emergency Medicine

No abstract provided.

Toward Directed Energy Planetary Defense, Philip Lubin, Gary B. Hughes, J Bible, Jesse Bublitz, Josh Arriola, Caio Motta, Jon Suen, Isabella Johansson, Jordan Riley, Nilou Sarvian, Deborah Clayton-Warwick, Jane Wu, Andrew Milich, Mitch Oleson, Mark Pryor, Peter Krogen, Miikka Kangas, Hugh O'Neill

Statistics

Asteroids and comets that cross Earth’s orbit pose a credible risk of impact, with potentially severe disturbances to Earth and society. We propose an orbital planetary defense system capable of heating the surface of potentially hazardous objects to the vaporization point as a feasible approach to impact risk mitigation. We call the system DE-STAR, for Directed Energy System for Targeting of Asteroids and exploration. The DESTAR is a modular-phased array of kilowatt class lasers powered by photovoltaics. Modular design allows for incremental development, minimizing risk, and allowing for technological codevelopment. An orbiting structure would be developed in stages. The main …

Statistical Analysis Of The Comet Assay Using A Mixture Of Gamma Distributions, Bryan E. Shepherd, Dr. G. Bruce Schaalje

Journal of Undergraduate Research

The comet (single cell gel electrophoresis) assay is a highly sensitive method of detecting cellular DNA damage that is often used in cancer research. The “tail moment” is the most widely used measurement of DNA damage in the comet assay. A higher tail moment indicates more DNA damage. In almost all cases the tail moments of a sample of cells do not follow the normal distribution, and often the variation of tail moments between samples of cells exposed to different treatments is unequal. This causes difficulty when performing statistical analyses because these assumptions are necessary in order for t-tests or …

Bayesian Model Averaging:- An Application In Cancer Clinical Trial, Atanu Bhattacharjee

COBRA Preprint Series

Data driven conclusion is mostly accepted approach in any medical research problem. In case of limited knowledge of deep idea about supportive data on the problem, automatic digging of the variable plays important role for insight view of the study. Bayesian model averaging can be considered for automatics variable selection. It can be used as an alternative of stepwise regression method. The aim of this paper is to show the application of Bayesian modeling averaging in medical research particularly in cancer trial. Method is illustrated on Bone marrow transplant data. It can be recommended that BMA can be used frequently …