Open Access. Powered by Scholars. Published by Universities.®

Biostatistics Commons

Open Access. Powered by Scholars. Published by Universities.®

2296 Full-Text Articles 3869 Authors 444591 Downloads 62 Institutions

All Articles in Biostatistics

Faceted Search

2296 full-text articles. Page 1 of 79.

Optimized Adaptive Enrichment Designs For Multi-Arm Trials: Learning Which Subpopulations Benefit From Different Treatments, Jon Arni Steingrimsson, Joshua Betz, Tiachen Qian, Michael Rosenblum 2017 Department of Biostatistics, Brown School of Public Health

Optimized Adaptive Enrichment Designs For Multi-Arm Trials: Learning Which Subpopulations Benefit From Different Treatments, Jon Arni Steingrimsson, Joshua Betz, Tiachen Qian, Michael Rosenblum

Johns Hopkins University, Dept. of Biostatistics Working Papers

We propose a class of adaptive randomized trial designs for comparing two treatments to a common control in two disjoint subpopulations. The type of adaptation, called adaptive enrichment, involves a preplanned rule for modifying enrollment and arm assignment based on accruing data in an ongoing trial. The motivation for this adaptive feature is that interim data may indicate that a subpopulation, such as those with lower disease severity at baseline, are unlikely to benefit from a particular treatment, while uncertainty remains for the other treatment and/or subpopulation. We developed a new multiple testing procedure tailored to this design problem ...


Using The Roc Curve To Measure Association And Evaluate Prediction Accuracy For A Binary Outcome, Jingjing Yin, Robert L. Vogel 2017 Georgia Southern University

Using The Roc Curve To Measure Association And Evaluate Prediction Accuracy For A Binary Outcome, Jingjing Yin, Robert L. Vogel

Jingjing Yin

This review article addresses the ROC curve and its advantage over the odds ratio to measure the association between a continuous variable and a binary outcome. A simple parametric model under the normality assumption and the method of Box-Cox transformation for non-normal data are discussed. Applications of the binormal model and the Box-Cox transformation under both univariate and multivariate inference are illustrated by a comprehensive data analysis tutorial. Finally, a summary and recommendations are given as to the usage of the binormal ROC curve.


Lung Flute Improves Symptoms And Health Status In Copd With Chronic Bronchitis A 26 Week Randomized Controlled Trial, Sanjay Sethi, Jingjing Yin, Pamela K. Anderson 2017 University of Buffalo

Lung Flute Improves Symptoms And Health Status In Copd With Chronic Bronchitis A 26 Week Randomized Controlled Trial, Sanjay Sethi, Jingjing Yin, Pamela K. Anderson

Jingjing Yin

Background: Chronic obstructive pulmonary disease (COPD) is characterized by mucus hypersecretion that contributes to disease related morbidity and is associated with increased mortality. The Lung Flute® is a new respiratory device that produces a low frequency acoustic wave with moderately vigorous exhalation to increase mucus clearance. We hypothesized that the Lung Flute, used on a twice daily basis will provide clinical benefit to patients with COPD with chronic bronchitis. Methods: We performed a 26 week randomized, non-intervention controlled, single center, open label trial in 69 patients with COPD and Chronic Bronchitis. The primary endpoint was change in respiratory symptoms measured ...


Evaluating The Efficiency Of Treatment Comparison In Crossover Design By Allocating Subjects Based On Ranked Auxiliary Variable, Yisong Huang, Hani Samawi, Robert Vogel, Jingjing Yin, Worlanyo E. Gato, Daniel Linder 2017 Georgia Southern University

Evaluating The Efficiency Of Treatment Comparison In Crossover Design By Allocating Subjects Based On Ranked Auxiliary Variable, Yisong Huang, Hani Samawi, Robert Vogel, Jingjing Yin, Worlanyo E. Gato, Daniel Linder

Jingjing Yin

The validity of statistical inference depends on proper randomization methods. However, even with proper randomization, we can have imbalanced with respect to important characteristics. In this paper, we introduce a method based on ranked auxiliary variables for treatment allocation in crossover designs using Latin squares models. We evaluate the improvement of the efficiency in treatment comparisons using the proposed method. Our simulation study reveals that our proposed method provides a more powerful test compared to simple randomization with the same sample size. The proposed method is illustrated by conducting an experiment to compare two different concentrations of titanium dioxide nanofiber ...


Estimation Of P(X > Y) When X And Y Are Dependent Random Variables Using Different Bivariate Sampling Schemes, Hani M. Samawi, Amal Helu, Haresh Rochani, Jingjing Yin, Daniel Linder 2017 Georgia Southern University

Estimation Of P(X > Y) When X And Y Are Dependent Random Variables Using Different Bivariate Sampling Schemes, Hani M. Samawi, Amal Helu, Haresh Rochani, Jingjing Yin, Daniel Linder

Jingjing Yin

The stress-strength models have been intensively investigated in the literature in regards of estimating the reliability θ = P (X > Y) using parametric and nonparametric approaches under different sampling schemes when X and Y are independent random variables. In this paper, we consider the problem of estimating θ when (X, Y) are dependent random variables with a bivariate underlying distribution. The empirical and kernel estimates of θ = P (X > Y), based on bivariate ranked set sampling (BVRSS) are considered, when (X, Y) are paired dependent continuous random variables. The estimators obtained are compared to their counterpart, bivariate simple random sampling (BVSRS ...


Constructing A Confidence Interval For The Fraction Who Benefit From Treatment, Using Randomized Trial Data, Emily J. Huang, Ethan X. Fang, Daniel F. Hanley, Michael Rosenblum 2017 Johns Hopkins University School of Public Health, Department of Biostatistics

Constructing A Confidence Interval For The Fraction Who Benefit From Treatment, Using Randomized Trial Data, Emily J. Huang, Ethan X. Fang, Daniel F. Hanley, Michael Rosenblum

Johns Hopkins University, Dept. of Biostatistics Working Papers

The fraction who benefit from treatment is the proportion of patients whose potential outcome under treatment is better than that under control. Inference on this parameter is challenging since it is only partially identifiable, even in our context of a randomized trial. We propose a new method for constructing a confidence interval for the fraction, when the outcome is ordinal or binary. Our confidence interval procedure is pointwise consistent. It does not require any assumptions about the joint distribution of the potential outcomes, although it has the flexibility to incorporate various user-defined assumptions. Unlike existing confidence interval methods for partially ...


Using Ranked Auxiliary Covariate As A More Efficient Sampling Design For Ancova Model: Analysis Of A Psychological Intervention To Buttress Resilience, Rajai Jabrah, Hani Samawi, Robert Vogel, Haresh Rochani, Daniel Linder 2017 Georgia Southern University

Using Ranked Auxiliary Covariate As A More Efficient Sampling Design For Ancova Model: Analysis Of A Psychological Intervention To Buttress Resilience, Rajai Jabrah, Hani Samawi, Robert Vogel, Haresh Rochani, Daniel Linder

Robert L. Vogel

Drawing a sample can be costly or time consuming in some studies. However, it may be possible to rank the sampling units according to some baseline auxiliary covariates, which are easily obtainable, and/or cost efficient. Ranked set sampling (RSS) is a method to achieve this goal. In this paper, we propose a modified approach of the RSS method to allocate units into an experimental study that compares L groups. Computer simulation estimates the empirical nominal values and the empirical power values for the test procedure of comparing L different groups using modified RSS based on the regression approach in ...


Evaluating The Efficiency Of Treatment Comparison In Crossover Design By Allocating Subjects Based On Ranked Auxiliary Variable, Yisong Huang, Hani Samawi, Robert Vogel, Jingjing Yin, Worlanyo E. Gato, Daniel Linder 2017 Georgia Southern University

Evaluating The Efficiency Of Treatment Comparison In Crossover Design By Allocating Subjects Based On Ranked Auxiliary Variable, Yisong Huang, Hani Samawi, Robert Vogel, Jingjing Yin, Worlanyo E. Gato, Daniel Linder

Robert L. Vogel

The validity of statistical inference depends on proper randomization methods. However, even with proper randomization, we can have imbalanced with respect to important characteristics. In this paper, we introduce a method based on ranked auxiliary variables for treatment allocation in crossover designs using Latin squares models. We evaluate the improvement of the efficiency in treatment comparisons using the proposed method. Our simulation study reveals that our proposed method provides a more powerful test compared to simple randomization with the same sample size. The proposed method is illustrated by conducting an experiment to compare two different concentrations of titanium dioxide nanofiber ...


Correction Of Verification Bias By Application Of Homogeneous Log-Linear Models For A Single Scale Binary Diagnostic Test, Haresh D. Rochani, Hani M. Samawi, Robert L. Vogel, Jingjing Yin 2017 Georgia Southern University

Correction Of Verification Bias By Application Of Homogeneous Log-Linear Models For A Single Scale Binary Diagnostic Test, Haresh D. Rochani, Hani M. Samawi, Robert L. Vogel, Jingjing Yin

Robert L. Vogel

In patient management and control of many infectious diseases it is very crucial to have accurate diagnostic test. The test/procedure that determines the true disease status without an error is referred to as gold standard test. Even when a gold standard exist, it is extremely difficult to verify each patient due to the issues of cost-effectiveness and invasive nature of the procedures. In practice some of the patients with test results are not selected for verification of the disease status which results into a verification bias for diagnostic tests. The ability of the diagnostic tests to correctly identify the ...


Persistent Organic Pollutants And Mortality In The United States, Nhanes 1999-2011., Kristiann Fry, Melinda C Power 2017 George Washington University

Persistent Organic Pollutants And Mortality In The United States, Nhanes 1999-2011., Kristiann Fry, Melinda C Power

Epidemiology and Biostatistics Faculty Publications

Background

Persistent organic pollutants (POPs) are environmentally and biologically persistent chemicals that include polybrominated diphenyl ethers (PBDEs), per- and polyfluoroalkyl substances (PFASs), polychlorinated biphenyls (PCBs), and organochlorine (OC) pesticides. Currently, data on the associations between exposure to POPs and the risk of mortality in the U.S. population is limited.

Our objective was to determine if higher exposure to POPs is associated with greater risk of all-cause, cancer, heart/cerebrovascular disease, or other-cause mortality.

Methods

Analyses included participants aged 60 years and older from the 1999–2006 National Health and Nutrition Examination Surveys (NHANES). We included 483 participants for analyses ...


Correction Of Verification Bias By Application Of Homogeneous Log-Linear Models For A Single Scale Binary Diagnostic Test, Haresh D. Rochani, Hani M. Samawi, Robert L. Vogel, Jingjing Yin 2017 Georgia Southern University

Correction Of Verification Bias By Application Of Homogeneous Log-Linear Models For A Single Scale Binary Diagnostic Test, Haresh D. Rochani, Hani M. Samawi, Robert L. Vogel, Jingjing Yin

Haresh Rochani

In patient management and control of many infectious diseases it is very crucial to have accurate diagnostic test. The test/procedure that determines the true disease status without an error is referred to as gold standard test. Even when a gold standard exist, it is extremely difficult to verify each patient due to the issues of cost-effectiveness and invasive nature of the procedures. In practice some of the patients with test results are not selected for verification of the disease status which results into a verification bias for diagnostic tests. The ability of the diagnostic tests to correctly identify the ...


Estimation Of P(X > Y) When X And Y Are Dependent Random Variables Using Different Bivariate Sampling Schemes, Hani M. Samawi, Amal Helu, Haresh Rochani, Jingjing Yin, Daniel Linder 2017 Georgia Southern University

Estimation Of P(X > Y) When X And Y Are Dependent Random Variables Using Different Bivariate Sampling Schemes, Hani M. Samawi, Amal Helu, Haresh Rochani, Jingjing Yin, Daniel Linder

Haresh Rochani

The stress-strength models have been intensively investigated in the literature in regards of estimating the reliability θ = P (X > Y) using parametric and nonparametric approaches under different sampling schemes when X and Y are independent random variables. In this paper, we consider the problem of estimating θ when (X, Y) are dependent random variables with a bivariate underlying distribution. The empirical and kernel estimates of θ = P (X > Y), based on bivariate ranked set sampling (BVRSS) are considered, when (X, Y) are paired dependent continuous random variables. The estimators obtained are compared to their counterpart, bivariate simple random sampling (BVSRS ...


Using Ranked Auxiliary Covariate As A More Efficient Sampling Design For Ancova Model: Analysis Of A Psychological Intervention To Buttress Resilience, Rajai Jabrah, Hani Samawi, Robert Vogel, Haresh Rochani, Daniel Linder 2017 Georgia Southern University

Using Ranked Auxiliary Covariate As A More Efficient Sampling Design For Ancova Model: Analysis Of A Psychological Intervention To Buttress Resilience, Rajai Jabrah, Hani Samawi, Robert Vogel, Haresh Rochani, Daniel Linder

Haresh Rochani

Drawing a sample can be costly or time consuming in some studies. However, it may be possible to rank the sampling units according to some baseline auxiliary covariates, which are easily obtainable, and/or cost efficient. Ranked set sampling (RSS) is a method to achieve this goal. In this paper, we propose a modified approach of the RSS method to allocate units into an experimental study that compares L groups. Computer simulation estimates the empirical nominal values and the empirical power values for the test procedure of comparing L different groups using modified RSS based on the regression approach in ...


Comparison Of Adaptive Randomized Trial Designs For Time-To-Event Outcomes That Expand Versus Restrict Enrollment Criteria, To Test Non-Inferiority, Josh Betz, Jon Arni Steingrimsson, Tianchen Qian, Michael Rosenblum 2017 Johns Hopkins Bloomberg School of Public Health, Department of Biostatistics

Comparison Of Adaptive Randomized Trial Designs For Time-To-Event Outcomes That Expand Versus Restrict Enrollment Criteria, To Test Non-Inferiority, Josh Betz, Jon Arni Steingrimsson, Tianchen Qian, Michael Rosenblum

Johns Hopkins University, Dept. of Biostatistics Working Papers

Adaptive enrichment designs involve preplanned rules for modifying patient enrollment criteria based on data accrued in an ongoing trial. These designs may be useful when it is suspected that a subpopulation, e.g., defined by a biomarker or risk score measured at baseline, may benefit more from treatment than the complementary subpopulation. We compare two types of such designs, for the case of two subpopulations that partition the overall population. The first type starts by enrolling the subpopulation where it is suspected the new treatment is most likely to work, and then may expand inclusion criteria if there is early ...


Using Ranked Auxiliary Covariate As A More Efficient Sampling Design For Ancova Model: Analysis Of A Psychological Intervention To Buttress Resilience, Rajai Jabrah, Hani Samawi, Robert Vogel, Haresh Rochani, Daniel Linder 2017 Georgia Southern University

Using Ranked Auxiliary Covariate As A More Efficient Sampling Design For Ancova Model: Analysis Of A Psychological Intervention To Buttress Resilience, Rajai Jabrah, Hani Samawi, Robert Vogel, Haresh Rochani, Daniel Linder

Hani M. Samawi

Drawing a sample can be costly or time consuming in some studies. However, it may be possible to rank the sampling units according to some baseline auxiliary covariates, which are easily obtainable, and/or cost efficient. Ranked set sampling (RSS) is a method to achieve this goal. In this paper, we propose a modified approach of the RSS method to allocate units into an experimental study that compares L groups. Computer simulation estimates the empirical nominal values and the empirical power values for the test procedure of comparing L different groups using modified RSS based on the regression approach in ...


Inference On Overlapping Coefficients In Two Exponential Populations, Mohammad F. Al-Saleh, Hani M. Samawi 2017 Yarmouk University

Inference On Overlapping Coefficients In Two Exponential Populations, Mohammad F. Al-Saleh, Hani M. Samawi

Hani M. Samawi

Three measures of overlap, namely Matusita’s measureρ , Morisita’s measure λ and Weitzman’s measure Δ are investigated in this article for two exponential populations with different means. It is well that the estimators of those measures of overlap are biased. The bias is of these estimators depends on the unknown overlap parameters. There are no closed-form, exact formulas, for those estimators variances or their exact sampling distributions. Monte Carlo evaluations are used to study the bias and precision of the proposed overlap measures. Bootstrap method and Taylor series approximation are used to construct confidence intervals for the overlap ...


Evaluating The Efficiency Of Treatment Comparison In Crossover Design By Allocating Subjects Based On Ranked Auxiliary Variable, Yisong Huang, Hani Samawi, Robert Vogel, Jingjing Yin, Worlanyo E. Gato, Daniel Linder 2017 Georgia Southern University

Evaluating The Efficiency Of Treatment Comparison In Crossover Design By Allocating Subjects Based On Ranked Auxiliary Variable, Yisong Huang, Hani Samawi, Robert Vogel, Jingjing Yin, Worlanyo E. Gato, Daniel Linder

Hani M. Samawi

The validity of statistical inference depends on proper randomization methods. However, even with proper randomization, we can have imbalanced with respect to important characteristics. In this paper, we introduce a method based on ranked auxiliary variables for treatment allocation in crossover designs using Latin squares models. We evaluate the improvement of the efficiency in treatment comparisons using the proposed method. Our simulation study reveals that our proposed method provides a more powerful test compared to simple randomization with the same sample size. The proposed method is illustrated by conducting an experiment to compare two different concentrations of titanium dioxide nanofiber ...


Estimation Of P(X > Y) When X And Y Are Dependent Random Variables Using Different Bivariate Sampling Schemes, Hani M. Samawi, Amal Helu, Haresh Rochani, Jingjing Yin, Daniel Linder 2017 Georgia Southern University

Estimation Of P(X > Y) When X And Y Are Dependent Random Variables Using Different Bivariate Sampling Schemes, Hani M. Samawi, Amal Helu, Haresh Rochani, Jingjing Yin, Daniel Linder

Hani M. Samawi

The stress-strength models have been intensively investigated in the literature in regards of estimating the reliability θ = P (X > Y) using parametric and nonparametric approaches under different sampling schemes when X and Y are independent random variables. In this paper, we consider the problem of estimating θ when (X, Y) are dependent random variables with a bivariate underlying distribution. The empirical and kernel estimates of θ = P (X > Y), based on bivariate ranked set sampling (BVRSS) are considered, when (X, Y) are paired dependent continuous random variables. The estimators obtained are compared to their counterpart, bivariate simple random sampling (BVSRS ...


Correction Of Verication Bias Using Log-Linear Models For A Single Binaryscale Diagnostic Tests, Haresh Rochani, Hani M. Samawi, Robert L. Vogel, Jingjing Yin 2017 Georgia Southern University

Correction Of Verication Bias Using Log-Linear Models For A Single Binaryscale Diagnostic Tests, Haresh Rochani, Hani M. Samawi, Robert L. Vogel, Jingjing Yin

Hani M. Samawi

In diagnostic medicine, the test that determines the true disease status without an error is referred to as the gold standard. Even when a gold standard exists, it is extremely difficult to verify each patient due to the issues of costeffectiveness and invasive nature of the procedures. In practice some of the patients with test results are not selected for verification of the disease status which results in verification bias for diagnostic tests. The ability of the diagnostic test to correctly identify the patients with and without the disease can be evaluated by measures such as sensitivity, specificity and predictive ...


Prevalence And Trends In Transmitted And Acquired Antiretroviral Drug Resistance, Washington, Dc, 1999-2014., Annette M Aldous, Amanda D Castel, David M Parenti 2017 George Washington University

Prevalence And Trends In Transmitted And Acquired Antiretroviral Drug Resistance, Washington, Dc, 1999-2014., Annette M Aldous, Amanda D Castel, David M Parenti

Epidemiology and Biostatistics Faculty Publications

Background

Drug resistance limits options for antiretroviral therapy (ART) and results in poorer health outcomes among HIV-infected persons. We sought to characterize resistance patterns and to identify predictors of resistance in Washington, DC.

Methods

We analyzed resistance in the DC Cohort, a longitudinal study of HIV-infected persons in care in Washington, DC. We measured cumulative drug resistance (CDR) among participants with any genotype between 1999 and 2014 (n = 3411), transmitted drug resistance (TDR) in ART-naïve persons (n = 1503), and acquired drug resistance (ADR) in persons with genotypes before and after ART initiation (n = 309). Using logistic regression, we assessed associations ...


Digital Commons powered by bepress