Statistics and Probability Commons^™

Identifying Influential Observations Through The Intraclass Correlation Coefficient, Angel De Jesus Davalos

Open Access Theses & Dissertations

In this thesis, we analyze the performance of adapting the DFBETA statistic for identifying influential observations on the intraclass correlation coefficient under the assumptions of the one-way random effects model. Additionally, we introduce an approach for transforming negative intraclass correlation coefficient estimation values using the method of moments estimator. We apply this method on a data set of repeated blood pressure measurements, after which we will investigate implications of identifying influential observations.

On The Eigenstructures Of Functional K-Potent Matrices And Their Integral Forms, Yan Wu, Daniel F. Linder

Biostatistics: Faculty Publications

In this paper, a functional k-potent matrix satisfies the equation, where k and r are positive integers, and are real numbers. This class of matrices includes idempotent, Nilpotent, and involutary matrices, and more. It turns out that the matrices in this group are best distinguished by their associated eigen-structures. The spectral properties of the matrices are exploited to construct integral k-potent matrices, which have special roles in digital image encryption.

A Markov Transition Model To Dementia With Death As A Competing Event, Liou Xu

University of Kentucky Doctoral Dissertations

The research on multi-state Markov transition model is motivated by the nature of the longitudinal data from the Nun Study (Snowdon, 1997), and similar information on the BRAiNS cohort (Salazar, 2004). Our goal is to develop a flexible methodology for handling the categorical longitudinal responses and competing risks time-to-event that characterizes the features of the data for research on dementia. To do so, we treat the survival from death as a continuous variable rather than defining death as a competing absorbing state to dementia. We assume that within each subject the survival component and the Markov process are linked by …

Serum Antibodies To Human Papillomavirus Type 6, 11, 16 And 18 And Their Role In The Natural History Of Hpv Infection In Men, Beibei Lu

USF Tampa Graduate Theses and Dissertations

Our understanding of humoral immune response to human papillomavirus (HPV) infection has been mainly derived from studies in women. Very little is known about humoral immune response to HPV in men. There is also a growing interest in understanding the burden of HPV exposure in the subgroups of the male population, including men who have sex with women (MSW), men who have sex with men (MSM) and men who have sex with both men and women (MSMW). This dissertation was undertaken to understand and characterize humoral immune response, measured by detectable serum antibody IgG, to HPV 6, 11, 16 and …

Inadequate Health Numeracy Affects Cancer Screening Practices In Vulnerable Populations, Sherrine Eid Mph, Dorothy Faulkner Phd

Administration & Leadership

No abstract provided.

Survival Analysis With Error-Prone Time-Varying Covariates: A Risk Set Calibration Approach, Xiaomei Liao, David M. Zucker, Yi Li, Donna Spiegelman

Harvard University Biostatistics Working Paper Series

No abstract provided.

A Comparison Of Frequentist And Bayesian Approaches To The Estimation Of Long-Stay Per-Diems, Jeff Hatcher, Jason M. Sutherland

Dartmouth Scholarship

Within many diagnosis related group (DRG) systems, there is recognition that a single cost weight per DRG is not suitable, and that cost weights should take into account extremely lengthy hospital stays. Long lengths of stay are considered to be due to factors largely beyond the control of the hospital, and a single weight per DRG would potentially place hospitals under financial risk.

Within Canada's acute-care, inpatient grouping methodology - Case Mix Groups (CMG+) - long-stay episodes represent approximately 4.5% of all discharges. Within a CMG (analogous to DRG), the cost weight assigned to long-stay cases consists of the typical …

Lot Quality Assurance Sampling (Lqas) And The Mozambique Malaria Indicator Surveys, Caitlin Biedron, Marcello Pagano, Bethany L. Hedt, Albert Kilian, Amy Ratcliffe, Samuel Mabunda, Joseph J. Valadez

Harvard University Biostatistics Working Paper Series

No abstract provided.

Analysis Of Subgroup Data In Clinical Trials, Kao-Tai Tsai, Karl E. Peace

Biostatistics: Faculty Presentations (2003-2018)

This conference abstract was published in the Proceedings of the Sixteenth Annual Biopharmaceutical Applied Statistics Symposium.

Causal Inference In Epidemiological Studies With Strong Confounding, Kelly L. Moore, Romain S. Neugebauer, Mark J. Van Der Laan, Ira B. Tager

U.C. Berkeley Division of Biostatistics Working Paper Series

One of the identifiabilty assumptions of causal effects defined by marginal structural model (MSM) parameters is the experimental treatment assignment (ETA) assumption. Practical violations of this assumption frequently occur in data analysis, when certain exposures are rarely observed within some strata of the population. The inverse probability of treatment weighted (IPTW) estimator is particularly sensitive to violations of this assumption, however, we demonstrate that this is a problem for all estimators of causal effects. This is due to the fact that the ETA assumption is about information (or lack thereof) in the data. A new class of causal models, causal …

Causal Inference For Nested Case-Control Studies Using Targeted Maximum Likelihood Estimation, Sherri Rose, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

A nested case-control study is conducted within a well-defined cohort arising out of a population of interest. This design is often used in epidemiology to reduce the costs associated with collecting data on the full cohort; however, the case control sample within the cohort is a biased sample. Methods for analyzing case-control studies have largely focused on logistic regression models that provide conditional and not marginal causal estimates of the odds ratio. We previously developed a Case-Control Weighted Targeted Maximum Likelihood Estimation (TMLE) procedure for case-control study designs, which relies on the prevalence probability q0. We propose the use of …

Impact Of Ambient Air Pollution On Survival Of Renal Transplant Recipients, Rhonda Kristine Hwang

Loma Linda University Electronic Theses, Dissertations & Projects

There is increasing evidence that ambient air pollution is associated with coronary heart disease morbidity and mortality. This research has focused on the general public and less so on possible sensitive subgroups even though these may have even greater susceptibility to adverse effects of ambient air pollution. With highly prevalent traditional as well as nontraditional risk factors, renal transplant recipients may potentially be a sensitive subgroup. The purpose of this study was to evaluate the possible effect of between long-term exposure to air pollution on the risk of CHD mortality among renal transplant recipients. This cohort study includes 32,239 adult, …

Study Of The Four Factor Theory Of Women’S Sexual Function, Julie M. Merrell

Loma Linda University Electronic Theses, Dissertations & Projects

Tiefer, Hall, and Tavris (2002) described factors comprising four categories of female sexual function. They suggested that unique factors need to be examined to understand sexual function in women. Socio-cultural, political, or economic factors, partner and relationship factors, psychological factors, and medical factors were described as aspects of women’s lives that can be the source of sexual dysfunction. In a previous study, Merrell (2007) utilized Tiefer et al’s (2002) four factor model of sexual functioning to examine female sexual functioning looking specifically at body shame, relationship satisfaction, positive and negative affect, sexual self-schema, and overall health. Based on the results …

The Effects Of Physical Activity And Nutrient Intake On The Risk Of Hip Fracture : Results From The Adventist Health Study-2, Wen-Ling Liao

Loma Linda University Electronic Theses, Dissertations & Projects

This is a two year of follow up study of Adventist Health Study-2 (AHS-2). We assessed the association between physical activity, nutrient intake and risk of hip fracture among peri- and post menopausal Caucasian women using unconditional logistic regression models. All subjects completed a lifestyle questionnaire which including information of physical activity and frequency and portion size of food intake at enrollment into the study (2002-2007). The “Bi-Annual Hospitalization History” questionnaire which included a question about hip fractures due to minor trauma/falls was sent to subjects approximately two years after enrollment, with a response rat of 82.84%. In this cohort, …

A Spatio-Temporal Approach For Estimating Chronic Effects Of Air Pollution, Sonja Greven, Francesca Dominici, Scott L. Zeger

Johns Hopkins University, Dept. of Biostatistics Working Papers

Estimating the health risks associated with air pollution exposure is of great importance in public health. In air pollution epidemiology, two study designs have been used mainly. Time series studies estimate acute risk associated with short-term exposure. They compare day-to-day variation of pollution concentrations and mortality rates, and have been criticized for potential confounding by time-varying covariates. Cohort studies estimate chronic effects associated with long-term exposure. They compare long-term average pollution concentrations and time-to-death across cities, and have been criticized for potential confounding by individual risk factors or city-level characteristics.

We propose a new study design and a statistical model, …

Spatial Cluster Detection For Repeatedly Measured Outcomes While Accounting For Residential History, Andrea J. Cook, Diane Gold, Yi Li

Harvard University Biostatistics Working Paper Series

No abstract provided.

Spatial Cluster Detection For Weighted Outcomes Using Cumulative Geographic Residuals, Andrea J. Cook, Yi Li, David Arterburn, Ram C. Tiwari

Harvard University Biostatistics Working Paper Series

No abstract provided.

A Machine-Learning Algorithm For Estimating And Ranking The Impact Of Environmental Risk Factors In Exploratory Epidemiological Studies, Jessica G. Young, Alan E. Hubbard, B Eskenazi, Nicholas P. Jewell

U.C. Berkeley Division of Biostatistics Working Paper Series

No abstract provided.

Anthropometric Parameters Of Under-Five Years Old Children With Different Dietary Habits In Ukambani Region : A Study In Eastern Rural Kenya, Hellen M. Ndiku

Loma Linda University Electronic Theses, Dissertations & Projects

The objective of this descriptive cross sectional study was to assess dietary intake and nutritional status of children under-five years in two rural sites of Eastern Kenya where the staple cereals may differ. A modified rapid, knowledge, practice and coverage (KPC) questionnaire and a 24-hr dietary recall form were used to collect the data. A total of 403 households were surveyed from four randomly selected divisions. This yielded 629 surrogate 24-hr dietary recalls of children < 5 years with 314 from Mwingi district and 315 from Makueni district (49 % boys and 51 % girls).

Statistical analysis was done using SPSS and SAS. Comparison of means was done using t- test and chi square was used for proportions. The 24-hr …

The Importance Of Scale For Spatial-Confounding Bias And Precision Of Spatial Regression Estimators, Christopher J. Paciorek

Harvard University Biostatistics Working Paper Series

Increasingly, regression models are used when residuals are spatially correlated. Prominent examples include studies in environmental epidemiology to understand the chronic health effects of pollutants. I consider the effects of residual spatial structure on the bias and precision of regression coefficients, developing a simple framework in which to understand the key issues and derive informative analytic results. When the spatial residual is induced by an unmeasured confounder, regression models with spatial random effects and closely-related models such as kriging and penalized splines are biased, even when the residual variance components are known. Analytic and simulation results show how the bias …

Smoking Enhances Risk For New External Genital Warts In Men, Dorothy J. Wiley, David Elashoff, Emmanuel V. Masongsong, Diane M. Harper

Dartmouth Scholarship

Repeat episodes of HPV-related external genital warts reflect recurring or new infections. No study before has been sufficiently powered to delineate how tobacco use, prior history of EGWs and HIV infection affect the risk for new EGWs. Behavioral, laboratory and examination data for 2,835 Multicenter AIDS Cohort Study participants examined at 21,519 semi-annual visits were evaluated. Fourteen percent (391/2835) of men reported or were diagnosed with EGWs at 3% (675/21,519) of study visits. Multivariate analyses showed smoking, prior episodes of EGWs, HIV infection and CD4+ T-lymphocyte count among the infected, each differentially influenced the risk for new EGWs.

Analysis Of Randomized Comparative Clinical Trial Data For Personalized Treatment Selections, Tianxi Cai, Lu Tian, Peggy H. Wong, L. J. Wei

Harvard University Biostatistics Working Paper Series

No abstract provided.

The Prevalence And Determinants Of Health Risk Behaviors Among High School Students In Mexico, Nellie León

Loma Linda University Electronic Theses, Dissertations & Projects

The Centers for Disease Control and Prevention report that despite health promotion efforts, adolescents continue to engage in behaviors that put them at risk for morbidity and mortality. Alcohol consumption, illicit drug use, smoking, and risky sexual behaviors are among the behaviors that contribute to leading causes of morbidity and mortality in youth; these four behaviors were explored in this study. An observational cross-sectional design was utilized. The Youth Risk Behavior Survey from the Centers for Disease Control and Prevention was utilized to assess the prevalence of the four risk behaviors among high school students in Jalisco, Mexico. Items constructed …

The Influence Of Familism On Descriptive And Injunctive Norms In Predicting The Intention To Eat A Vegetarian Diet Among Chinese Seventh-Day Adventists, See Wei Toh

Loma Linda University Electronic Theses, Dissertations & Projects

According to the theory of planned behavior (TpB), one determinant of intention to engage in a behavior is the subjective norm. Various studies have found that subjective norm is often the weaker predictor of intention compared to perceived behavioral control and attitude. This study examined whether familism (emphasis on the family rather than the individual) would contribute positively to the predictive power of the TpB model through interactions with the family portion of descriptive and injunctive norms. Descriptive and injunctive norms are component variables of the subjective norm. A sample of 284 adult Chinese Seventh-day Adventists 18 years and older …

Complete Identification Of Permissible Sampling Rates For First-Order Sampling Of Multi-Band Bandpass Signals, Yan Wu, Daniel F. Linder

Biostatistics: Faculty Publications

The first-order sampling of multi-band bandpass signals with arbitrary band positions is considered in this paper. Gaps between the spectral sub-bands are utilized to achieve lower sampling rates than the Nyquist. The lowest possible sampling rate along with other permissible sampling rates is identified via a unique partition of the frequency axis. With the complete identification of all the permissible sampling rates, a necessary and sufficient sampling theorem for multi-band bandpass signals is presented in terms of a series of csinc-interpolators.

A Small Sample Correction For Estimating Attributable Risk In Case-Control Studies, Daniel B. Rubin

U.C. Berkeley Division of Biostatistics Working Paper Series

The attributable risk, often called the population attributable risk, is in many epidemiological contexts a more relevant measure of exposure-disease association than the excess risk, relative risk, or odds ratio. When estimating attributable risk with case-control data and a rare disease, we present a simple correction to the standard approach making it essentially unbiased, and also less noisy. As with analogous corrections given in Jewell (1986) for other measures of association, the adjustment often won't make a substantial difference unless the sample size is very small or point estimates are desired within fine strata, but we discuss the possible utility …

Spatial Misalignment In Time Series Studies Of Air Pollution And Health Data, Roger D. Peng, Michelle L. Bell

Johns Hopkins University, Dept. of Biostatistics Working Papers

Time series studies of environmental exposures often involve comparing daily changes in a toxicant measured at a point in space with daily changes in an aggregate measure of health. Spatial misalignment of the exposure and response variables can bias the estimation of health risk and the magnitude of this bias depends on the spatial variation of the exposure of interest. In air pollution epidemiology, there is an increasing focus on estimating the health effects of the chemical components of particulate matter. One issue that is raised by this new focus is the spatial misalignment error introduced by the lack of …

Calibrating Parametric Subject-Specific Risk Estimation, Tianxi Cai, Lu Tian, Hajime Uno, Scott D. Solomon, L. J. Wei

Harvard University Biostatistics Working Paper Series

No abstract provided.

Evaluating Subject-Level Incremental Values Of New Markers For Risk Classification Rule, Tianxi Cai, Lu Tian, Donald M. Lloyd-Jones, L. J. Wei

Harvard University Biostatistics Working Paper Series

No abstract provided.

The Association Of Maternal Intention To Breastfeed, Early Skin-To-Skin Mother/Infant Contact, And Exclusive Breastfeeding During The Maternity Hospital Stay, Leslie Mary Bramson

Loma Linda University Electronic Theses, Dissertations & Projects

Breastfeeding is the optimal method to nourish and nurture an infant. Exclusive breastfeeding rates in the United States have reached the goal of Healthy People 2010 that 75% of mother's breastfeed in the immediate postpartum period. Yet, less than 35% of San Bernardino county mothers and 47.7% of Riverside county mothers are exclusively breastfeeding during their maternity hospital stays, with as many as 50% of the infants being weaned from the breast in the first 14 days of life.

This prospective study examined archived data collected by Perinatal Services Network (PSN) of Loma Linda University Medical Center/Children's Hospital for the …