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Biometrical Journal. Biometrische Zeitschrift

Aldo Solari
No abstract text is available yet for this article.
April 21, 2017: Biometrical Journal. Biometrische Zeitschrift
Peter Bauer
No abstract text is available yet for this article.
April 21, 2017: Biometrical Journal. Biometrische Zeitschrift
Gino B Kpogbezan, Aad W van der Vaart, Wessel N van Wieringen, Gwenaël G R Leday, Mark A van de Wiel
Reconstruction of a high-dimensional network may benefit substantially from the inclusion of prior knowledge on the network topology. In the case of gene interaction networks such knowledge may come for instance from pathway repositories like KEGG, or be inferred from data of a pilot study. The Bayesian framework provides a natural means of including such prior knowledge. Based on a Bayesian Simultaneous Equation Model, we develop an appealing Empirical Bayes (EB) procedure that automatically assesses the agreement of the used prior knowledge with the data at hand...
April 10, 2017: Biometrical Journal. Biometrische Zeitschrift
Dong Xi, Ekkehard Glimm, Willi Maurer, Frank Bretz
We describe a general framework for weighted parametric multiple test procedures based on the closure principle. We utilize general weighting strategies that can reflect complex study objectives and include many procedures in the literature as special cases. The proposed weighted parametric tests bridge the gap between rejection rules using either adjusted significance levels or adjusted p-values. This connection is made by allowing intersection hypotheses of the underlying closed test procedure to be tested at level smaller than α...
March 29, 2017: Biometrical Journal. Biometrische Zeitschrift
Renata T C Yokota, Herman Van Oyen, Caspar W N Looman, Wilma J Nusselder, Martin Otava, Yimer Wasihun Kifle, Geert Molenberghs
Population aging is accompanied by the burden of chronic diseases and disability. Chronic diseases are among the main causes of disability, which is associated with poor quality of life and high health care costs in the elderly. The identification of which chronic diseases contribute most to the disability prevalence is important to reduce the burden. Although longitudinal studies can be considered the gold standard to assess the causes of disability, they are costly and often with restricted sample size. Thus, the use of cross-sectional data under certain assumptions has become a popular alternative...
March 23, 2017: Biometrical Journal. Biometrische Zeitschrift
Elisabeth Waldmann, David Taylor-Robinson, Nadja Klein, Thomas Kneib, Tania Pressler, Matthias Schmid, Andreas Mayr
Joint models for longitudinal and time-to-event data have gained a lot of attention in the last few years as they are a helpful technique clinical studies where longitudinal outcomes are recorded alongside event times. Those two processes are often linked and the two outcomes should thus be modeled jointly in order to prevent the potential bias introduced by independent modeling. Commonly, joint models are estimated in likelihood-based expectation maximization or Bayesian approaches using frameworks where variable selection is problematic and that do not immediately work for high-dimensional data...
March 21, 2017: Biometrical Journal. Biometrische Zeitschrift
Daiane Aparecida Zuanetti, Luis Aparecido Milan
We present a generalization of the usual (independent) mixture model to accommodate a Markovian first-order mixing distribution. We propose the data-driven reversible jump, a Markov chain Monte Carlo (MCMC) procedure, for estimating the a posteriori probability for each model in a model selection procedure and estimating the corresponding parameters. Simulated datasets show excellent performance of the proposed method in the convergence, model selection, and precision of parameters estimates. Finally, we apply the proposed method to analyze USA diabetes incidence datasets...
March 21, 2017: Biometrical Journal. Biometrische Zeitschrift
Moreno Ursino, Sarah Zohar, Frederike Lentz, Corinne Alberti, Tim Friede, Nigel Stallard, Emmanuelle Comets
The aim of phase I clinical trials is to obtain reliable information on safety, tolerability, pharmacokinetics (PK), and mechanism of action of drugs with the objective of determining the maximum tolerated dose (MTD). In most phase I studies, dose-finding and PK analysis are done separately and no attempt is made to combine them during dose allocation. In cases such as rare diseases, paediatrics, and studies in a biomarker-defined subgroup of a defined population, the available population size will limit the number of possible clinical trials that can be conducted...
March 21, 2017: Biometrical Journal. Biometrische Zeitschrift
Jinzhong Liu, Siva Sivaganesan, Purushottam W Laud, Peter Müller
We develop a Bayesian approach to subgroup analysis using ANOVA models with multiple covariates, extending an earlier work. We assume a two-arm clinical trial with normally distributed response variable. We also assume that the covariates for subgroup finding are categorical and are a priori specified, and parsimonious easy-to-interpret subgroups are preferable. We represent the subgroups of interest by a collection of models and use a model selection approach to finding subgroups with heterogeneous effects...
March 20, 2017: Biometrical Journal. Biometrische Zeitschrift
Jingheng Cai, Haijin He, Xinyuan Song, Liuquan Sun
Many studies have focused on determining the effect of the body mass index (BMI) on the mortality in different cohorts. In this article, we propose an additive-multiplicative mean residual life (MRL) model to assess the effects of BMI and other risk factors on the MRL function of survival time in a cohort of Chinese type 2 diabetic patients. The proposed model can simultaneously manage additive and multiplicative risk factors and provide a comprehensible interpretation of their effects on the MRL function of interest...
March 8, 2017: Biometrical Journal. Biometrische Zeitschrift
Xin Gao, Yurong R Cao, Nicholas Ogden, Louise Aubin, Huaiping P Zhu
A mixture Markov regression model is proposed to analyze heterogeneous time series data. Mixture quasi-likelihood is formulated to model time series with mixture components and exogenous variables. The parameters are estimated by quasi-likelihood estimating equations. A modified EM algorithm is developed for the mixture time series model. The model and proposed algorithm are tested on simulated data and applied to mosquito surveillance data in Peel Region, Canada.
March 6, 2017: Biometrical Journal. Biometrische Zeitschrift
Christina Beisel, Axel Benner, Christina Kunz, Annette Kopp-Schneider
When analyzing clinical trials with a stratified population, homogeneity of treatment effects is a common assumption in survival analysis. However, in the context of recent developments in clinical trial design, which aim to test multiple targeted therapies in corresponding subpopulations simultaneously, the assumption that there is no treatment-by-stratum interaction seems inappropriate. It becomes an issue if the expected sample size of the strata makes it unfeasible to analyze the trial arms individually...
March 6, 2017: Biometrical Journal. Biometrische Zeitschrift
Simina M Boca, Ruth M Pfeiffer, Joshua N Sampson
Meta-analysis can average estimates of multiple parameters, such as a treatment's effect on multiple outcomes, across studies. Univariate meta-analysis (UVMA) considers each parameter individually, while multivariate meta-analysis (MVMA) considers the parameters jointly and accounts for the correlation between their estimates. The performance of MVMA and UVMA has been extensively compared in scenarios with two parameters. Our objective is to compare the performance of MVMA and UVMA as the number of parameters, p, increases...
February 14, 2017: Biometrical Journal. Biometrische Zeitschrift
Mahmoud Torabi
In this paper, our aim is to analyze geographical and temporal variability of disease incidence when spatio-temporal count data have excess zeros. To that end, we consider random effects in zero-inflated Poisson models to investigate geographical and temporal patterns of disease incidence. Spatio-temporal models that employ conditionally autoregressive smoothing across the spatial dimension and B-spline smoothing over the temporal dimension are proposed. The analysis of these complex models is computationally difficult from the frequentist perspective...
February 10, 2017: Biometrical Journal. Biometrische Zeitschrift
Gaelle Saint-Hilary, Stephanie Cadour, Veronique Robert, Mauro Gasparini
Quantitative methodologies have been proposed to support decision making in drug development and monitoring. In particular, multicriteria decision analysis (MCDA) and stochastic multicriteria acceptability analysis (SMAA) are useful tools to assess the benefit-risk ratio of medicines according to the performances of the treatments on several criteria, accounting for the preferences of the decision makers regarding the relative importance of these criteria. However, even in its probabilistic form, MCDA requires the exact elicitations of the weights of the criteria by the decision makers, which may be difficult to achieve in practice...
February 10, 2017: Biometrical Journal. Biometrische Zeitschrift
Marilena Flouri, Shuyan Zhai, Thomas Mathew, Ionut Bebu
This paper addresses the problem of deriving one-sided tolerance limits and two-sided tolerance intervals for a ratio of two random variables that follow a bivariate normal distribution, or a lognormal/normal distribution. The methodology that is developed uses nonparametric tolerance limits based on a parametric bootstrap sample, coupled with a bootstrap calibration in order to improve accuracy. The methodology is also adopted for computing confidence limits for the median of the ratio random variable. Numerical results are reported to demonstrate the accuracy of the proposed approach...
February 9, 2017: Biometrical Journal. Biometrische Zeitschrift
Minjin Kim, Myunghee Cho Paik, Jiyeong Jang, Ying K Cheung, Joshua Willey, Mitchell S V Elkind, Ralph L Sacco
When analyzing time-to-event cohort data, two different ways of choosing a time scale have been discussed in the literature: time-on-study or age at onset of disease. One advantage of choosing the latter is interpretability of the hazard ratio as a function of age. To handle the analysis of age at onset in a principled manner, we present an analysis of the Cox Proportional Hazards model with time-varying coefficient for left-truncated and right-censored data. In the analysis of Northern Manhattan Study (NOMAS) with age at onset of stroke as outcome, we demonstrate that well-established risk factors may be important only around a certain age span and less established risk factors can have a strong effect in a certain age span...
February 3, 2017: Biometrical Journal. Biometrische Zeitschrift
Andrea Riebler, Leonhard Held
The projection of age-stratified cancer incidence and mortality rates is of great interest due to demographic changes, but also therapeutical and diagnostic developments. Bayesian age-period-cohort (APC) models are well suited for the analysis of such data, but are not yet used in routine practice of epidemiologists. Reasons may include that Bayesian APC models have been criticized to produce too wide prediction intervals. Furthermore, the fitting of Bayesian APC models is usually done using Markov chain Monte Carlo (MCMC), which introduces complex convergence concerns and may be subject to additional technical problems...
January 31, 2017: Biometrical Journal. Biometrische Zeitschrift
Martin Schumacher
No abstract text is available yet for this article.
January 27, 2017: Biometrical Journal. Biometrische Zeitschrift
Patrícia L Espinheira, Evelyne G Santos, Francisco Cribari-Neto
We proposed a new residual to be used in linear and nonlinear beta regressions. Unlike the residuals that had already been proposed, the derivation of the new residual takes into account not only information relative to the estimation of the mean submodel but also takes into account information obtained from the precision submodel. This is an advantage of the residual we introduced. Additionally, the new residual is computationally less intensive than the weighted residual. Recall that the computation of the latter involves an n×n matrix, where n is the sample size...
January 27, 2017: Biometrical Journal. Biometrische Zeitschrift
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