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Controlling for time-dependent confounding using marginal structural models AgEcon
Fewell, Zoe; Hernan, Miguel A.; Wolfe, Frederick; Tilling, Kate; Choi, Hyon; Sterne, Jonathan A.C..
Longitudinal studies in which exposures, confounders, and outcomes are measured repeatedly over time have the potential to allow causal inferences about the effects of exposure on outcome. There is particular interest in estimating the causal effects of medical treatments (or other interventions) in circumstances in which a randomized controlled trial is difficult or impossible. However, standard methods for estimating exposure effects in longitudinal studies are biased in the presence of time-dependent confounders affected by prior treatment. This article describes the use of marginal structural models (described by Robins, Hernán, and Brumback [2000]) to estimate exposure or treatment effects in the presence of time-dependent confounders affected by...
Tipo: Journal Article Palavras-chave: Marginal structural models; Causal models; Weighted regression; Survival analysis; Logistic regression; Confounding; Research Methods/ Statistical Methods.
Ano: 2004 URL: http://purl.umn.edu/116267
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Two postestimation commands for assessing confounding effects in epidemiological studies AgEcon
Wang, Zhiqiang.
Confounding is a major issue in observational epidemiological studies. This paper describes two postestimation commands for assessing confounding effects. One command (confall) displays and plots all possible effect estimates against one of p-value, Akaike information criterion, or Bayesian information criterion. This computing-intensive procedure allows researchers to inspect the variability of the effect estimates from various possible models. Another command (chest) uses a stepwise approach to identify variables that have substantially changed the effect estimate. Both commands can be used after most common estimation commands in epidemiological studies, such as logistic regression, conditional logistic regression, Poisson regression, linear regression,...
Tipo: Article Palavras-chave: Confall; Confgr; Chest; Epidemiological methods; Confounding; All possible effects; Change in estimate; Research Methods/ Statistical Methods.
Ano: 2007 URL: http://purl.umn.edu/119267
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Implementing double-robust estimators of causal effects AgEcon
Emsley, Richard; Lunt, Mark; Pickles, Andrew; Dunn, Graham.
This article describes the implementation of a double-robust estimator for pretest–posttest studies (Lunceford and Davidian, 2004, Statistics in Medicine 23: 2937–2960) and presents a new Stata command (dr) that carries out the procedure. A double-robust estimator gives the analyst two opportunities for obtaining unbiased inference when adjusting for selection effects such as confounding by allowing for different forms of model misspecification; a double-robust estimator also can offer increased efficiency when all the models are correctly specified. We demonstrate the results with a Monte Carlo simulation study, and we show how to implement the double-robust estimator on a single simulated dataset, both manually and by using the dr command.
Tipo: Article Palavras-chave: Dr; Double-robust estimators; Causal models; Confounding; Inverse probability of treatment weights; Propensity score; Research Methods/ Statistical Methods.
Ano: 2008 URL: http://purl.umn.edu/122597
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