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603 results on '"Woolson, Robert F"'

108. Chlorinated drinking water and bladder cancer: effect of misclassification on risk estimates

Author

Lynch, Charles F., Woolson, Robert F., O'Gorman, Thomas, and Cantor, Kenneth P.

Subjects
Chlorine -- Physiological aspects, Epidemiological research -- Methods, Bladder cancer -- Risk factors, Drinking water -- Composition, Environmental health -- Case studies, Environmental issues, Health
Abstract

Over the past decade studies have tried to evaluate the association between chlorinated water drinking and various cancers (e.g., bladder, colon, rectal). Chlorine is widely used as a water disinfectant. Its potential as a carcinogen was raised because it promotes the formation of trihalomethanes (carcinogenic substances) in water. Other studies that relate the consumption of chlorinated water with cancer have misclassified the odds for developing cancer (for both case and control groups under evaluation). This study demonstrates that bladder cancer risk increases as a function of the duration of drinking chlorinated water. Researchers found that the more information that was used about a participant (e.g., sources of drinking water) the higher were the risk estimates for chlorinated drinking water exposure. Although odds ratios for developing cancer increased as the numbers of years of exposure increased, these odds were generally low. Researchers also noted that errors of this type are common in environmental epidemiology studies; they suggest that health risks related to substances in the environment should be interpreted with caution, particularly if the potential for random misclassification of the exposure variable (in this case chlorine) exists. (Consumer Summary produced by Reliance Medical Information, Inc.)

Published
1989

114. Slope estimation for informatively right censored longitudinal data modelling the number of observations using geometric and Poisson distributions: application to renal transplant cohort.

Author

Jaffa, Miran A., Lipsitz, Stuart, and Woolson, Robert F.

Subjects
KIDNEY transplantation, LONGITUDINAL method, DATA modeling, GEOMETRIC analysis, POISSON distribution, MAXIMUM likelihood statistics, PROBABILITY theory, RESEARCH funding, STATISTICS, DATA analysis, TREATMENT effectiveness, RESEARCH bias, STATISTICAL models
Abstract

Analysis of longitudinal data is often complicated by the presence of informative right censoring. This type of censoring should be accounted for in the analysis so that valid slope estimates are attained. In this study, we developed a new likelihood-based approach wherein the likelihood function is integrated over random effects to obtain a marginal likelihood function. Maximum likelihood estimates for the population slope were acquired by direct maximisation of the marginal likelihood function and empirical Bayes estimates for the individual slopes were generated using Gaussian quadrature. The performance of the model was assessed using the geometric and Poisson distributions to model the number of observations for every individual subject. Our model generated valid estimates for the slopes under both distributions with minimal bias and mean squared errors. Our sensitivity analysis confirmed the robustness of the model to assumptions pertaining to the underlying distribution and demonstrated its insensitivity to normality assumptions. Moreover, superiority of the model in terms of accuracy of slope estimates was consistently shown across the different levels of censoring in comparison to the naïve and bootstrap approaches. This model was illustrated using the cohort of renal transplant patients and estimates of the slopes that are adjusted for informative right censoring were acquired. [ABSTRACT FROM AUTHOR]

Published
2015
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118. Modafinil and Cocaine Interactions

Author

Malcolm, Robert, primary, Swayngim, Karla, additional, Donovan, Jennifer L., additional, DeVane, C. Lindsay, additional, Elkashef, Ahmed, additional, Chiang, Nora, additional, Khan, Roberta, additional, Mojsiak, Jurij, additional, Myrick, Donald L., additional, Hedden, Sarra, additional, Cochran, Kristi, additional, and Woolson, Robert F., additional

Published
2006
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127. Safety Assessment in Pilot Studies When Zero Events Are Observed.

Author

Auget, Jean-Louis, Balakrishnan, N., Mesbah, Mounir, Molenberghs, Geert, Carter, Rickey E., and Woolson, Robert F.

Abstract

Pilot studies in clinical research settings frequently focus on estimating the frequency of occurrence of certain adverse events. When zero such events are observed, the question of legitimate inference on the true event rate arises. The relationship between binomial and geometric distributions' confidence intervals yields two useful graphical displays and interpretations for the event rate inference in this circumstance. The interval is also closely related to the Bayesian credible interval when the prior distribution for the event rate is uniform. In addition, the simple algebraic expression for the confidence bound is seen to be useful in the context of planning studies. [ABSTRACT FROM AUTHOR]

Published
2007
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148. Analysis of Categorized Data: Use of the Odds Ratio as a Measure of Association.

Author

Hillis, Stephen L. and Woolson, Robert F.

Subjects
PUBLIC health, SOCIAL science research, EPIDEMIOLOGY, EMPIRICAL research, MEDICAL research
Abstract

The authors discuss the use of the odds ratio as a measure of association between two dichotomous variables that typically indicate the presence or absence of a specific characteristic. A brief discussion of the three possible sampling methods: cross-sectional study, prospective study and retrospective (or case-control) study is included. [ABSTRACT FROM PUBLISHER]

Published
2002

149. Methods in Psychiatric Genetics.

Author

Hillis, Stephen L. and Woolson, Robert F.

Subjects
CHROMOSOMES, GENETICS, PUBLIC health, EPIDEMIOLOGY, MEDICAL research, PSYCHIATRY
Abstract

This chapter introduces the methods necessary for the readers to achieve their scientific goals and provide references for more advanced studies of particular issues. A discussion of genetics is also included. The appendix contains a brief glossary of some of the genetic and statistical terms used in this chapter. [ABSTRACT FROM PUBLISHER]

Published
2002

150. The reply

Author

Doebbeling, Bradley N, primary, Clarke, William R, additional, Watson, David, additional, Torner, James C, additional, Woolson, Robert F, additional, Voelker, Margaret D, additional, Barrett, Drue H, additional, and Schwartz, David A, additional

Published
2000
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