Nonlinear association structures in flexible Bayesian additive joint models
Statistics in Medicine, EarlyView. (Source: Statistics in Medicine)
Source: Statistics in Medicine - October 11, 2018 Category: Statistics Authors: Meike K öhler,
Nikolaus Umlauf,
Sonja Greven Source Type: research
Optimizing and evaluating biomarker combinations as trial ‐level general surrogates
Statistics in Medicine, EarlyView. (Source: Statistics in Medicine)
Source: Statistics in Medicine - October 11, 2018 Category: Statistics Authors: Erin E. Gabriel,
Michael C. Sachs,
Michael J. Daniels,
M. Elizabeth Halloran Source Type: research
Model averaging for robust extrapolation in evidence synthesis
Extrapolation from a source to a target, eg, from adults to children, is a promising approach to utilize external information when data are sparse. In the context of meta ‐analyses, one is commonly faced with a small number of studies, whereas potentially relevant additional information may also be available. Here, we describe a simple extrapolation strategy using heavy‐tailed mixture priors for effect estimation in meta‐analysis, which effectively results in a model‐averaging technique. The described method is robust in the sense that a potential prior‐data conflict, ie, a discrepancy between source and target d...
Source: Statistics in Medicine - October 10, 2018 Category: Statistics Authors: Christian R över,
Simon Wandel,
Tim Friede Tags: RESEARCH ARTICLE Source Type: research
Nonlinear association structures in flexible Bayesian additive joint models
We present an extended framework of flexible additive joint models that allows the estimation of nonlinear covariate specific associations by making use of Bayesian P ‐splines. Our joint models are estimated in a Bayesian framework using structured additive predictors for all model components, allowing for great flexibility in the specification of smooth nonlinear, time‐varying, and random effects terms for longitudinal submodel, survival submodel, and their association. The ability to capture truly linear and nonlinear associations is assessed in simulations and illustrated on the widely studied biomedical data on the...
Source: Statistics in Medicine - October 10, 2018 Category: Statistics Authors: Meike K öhler,
Nikolaus Umlauf,
Sonja Greven Tags: RESEARCH ARTICLE Source Type: research
Optimizing and evaluating biomarker combinations as trial ‐level general surrogates
We extend the method proposed in a recent work by the Authors for trial ‐level general surrogate evaluation to allow combinations of biomarkers and provide a procedure for finding the “best” combination of biomarkers based on the absolute prediction error summary of surrogate quality. We use a nonparametric Bayesian model that allows us to select an optimal subset of biomarkers without having to consider a large number of explicit model specifications for that subset. This dramatically reduces the number of model comparisons needed. Given the model's flexibility, complex nonlinear relationships can be fit when enough...
Source: Statistics in Medicine - October 10, 2018 Category: Statistics Authors: Erin E. Gabriel,
Michael C. Sachs,
Michael J. Daniels,
M. Elizabeth Halloran Tags: RESEARCH ARTICLE Source Type: research
Model averaging for robust extrapolation in evidence synthesis
Statistics in Medicine, EarlyView. (Source: Statistics in Medicine)
Source: Statistics in Medicine - October 10, 2018 Category: Statistics Authors: Christian R över,
Simon Wandel,
Tim Friede Source Type: research
Doubly robust estimation of the weighted average treatment effect for a target population
Statistics in Medicine, EarlyView. (Source: Statistics in Medicine)
Source: Statistics in Medicine - October 10, 2018 Category: Statistics Authors: Yebin Tao,
Haoda Fu Source Type: research
Power analysis for multivariable Cox regression models
Statistics in Medicine, EarlyView. (Source: Statistics in Medicine)
Source: Statistics in Medicine - October 10, 2018 Category: Statistics Authors: Emil Scosyrev,
Ekkehard Glimm Source Type: research
Power analysis for multivariable Cox regression models
In power analysis for multivariable Cox regression models, variance of the estimated log ‐hazard ratio for the treatment effect is usually approximated by inverting the expected null information matrix. Because, in many typical power analysis settings, assumed true values of the hazard ratios are not necessarily close to unity, the accuracy of this approximation is not theoretically g uaranteed. To address this problem, the null variance expression in power calculations can be replaced with one of the alternative expressions derived under the assumed true value of the hazard ratio for the treatment effect. This approach ...
Source: Statistics in Medicine - October 9, 2018 Category: Statistics Authors: Emil Scosyrev,
Ekkehard Glimm Tags: RESEARCH ARTICLE Source Type: research
Doubly robust estimation of the weighted average treatment effect for a target population
The weighted average treatment effect is a causal measure for the comparison of interventions in a specific target population, which may be different from the population where data are sampled from. For instance, when the goal is to introduce a new treatment to a target population, the question is what efficacy (or effectiveness) can be gained by switching patients from a standard of care (control) to this new treatment, for which the average treatment effect for the control estimand can be applied. In this paper, we propose two estimators based on augmented inverse probability weighting to estimate the weighted average tr...
Source: Statistics in Medicine - October 9, 2018 Category: Statistics Authors: Yebin Tao,
Haoda Fu Tags: RESEARCH ARTICLE Source Type: research
Optimal sample size planning for the Wilcoxon ‐Mann‐Whitney test
Statistics in Medicine, EarlyView. (Source: Statistics in Medicine)
Source: Statistics in Medicine - October 9, 2018 Category: Statistics Authors: Martin Happ,
Arne C. Bathke,
Edgar Brunner Source Type: research
Power and sample size requirements for GEE analyses of cluster randomized crossover trials
Statistics in Medicine, EarlyView. (Source: Statistics in Medicine)
Source: Statistics in Medicine - October 9, 2018 Category: Statistics Authors: Fan Li,
Andrew B. Forbes,
Elizabeth L. Turner,
John S. Preisser Source Type: research
Copula selection models for non ‐Gaussian outcomes that are missing not at random
Statistics in Medicine, EarlyView. (Source: Statistics in Medicine)
Source: Statistics in Medicine - October 9, 2018 Category: Statistics Authors: Manuel Gomes,
Rosalba Radice,
Jose Camarena Brenes,
Giampiero Marra Source Type: research
Optimal sample size planning for the Wilcoxon ‐Mann‐Whitney test
We present a unified approach that covers metric data with and without ties, count data, ordered categorical data, and even dichotomous data. For that, we calculate the unknown theoretical quantities such as the variances under the null and relevant alternative hypothesis by considering the following “synthetic data” approach. We evaluate data whose empirical distribution functions match the theoretical distribution functions involved in the computations of the unknown theoretical quantities. Then, well‐known relations for the ranks of the data are used for the calculations.In addition to computing the necessary samp...
Source: Statistics in Medicine - October 8, 2018 Category: Statistics Authors: Martin Happ,
Arne C. Bathke,
Edgar Brunner Tags: RESEARCH ARTICLE Source Type: research
Power and sample size requirements for GEE analyses of cluster randomized crossover trials
The cluster randomized crossover design has been proposed to improve efficiency over the traditional parallel cluster randomized design, which often involves a limited number of clusters. In recent years, the cluster randomized crossover design has been increasingly used to evaluate the effectiveness of health care policy or programs, and the interest often lies in quantifying the population ‐averaged intervention effect. In this paper, we consider the two‐treatment two‐period crossover design, and develop sample size procedures for continuous and binary outcomes corresponding to a population‐averaged model estimat...
Source: Statistics in Medicine - October 8, 2018 Category: Statistics Authors: Fan Li,
Andrew B. Forbes,
Elizabeth L. Turner,
John S. Preisser Tags: RESEARCH ARTICLE Source Type: research
