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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
Lucy X Kerns
In risk assessment, it is often desired to make inferences on the low dose levels at which a specific benchmark risk is attained. Applications of simultaneous hyperbolic confidence bands for low-dose risk estimation with quantal data under different dose-response models (multistage, Abbott-adjusted Weibull, and Abbott-adjusted log-logistic models) have appeared in the literature. The use of simultaneous three-segment bands under the multistage model has also been proposed recently. In this article, we present explicit formulas for constructing asymptotic one-sided simultaneous hyperbolic and three-segment bands for the simple log-logistic regression model...
January 27, 2017: Biometrical Journal. Biometrische Zeitschrift
Whitney P Ford, Philip M Westgate
Cluster randomized trials (CRTs) are studies in which clusters of subjects are randomized to different trial arms. Due to the nature of outcomes within the same cluster to be correlated, generalized estimating equations (GEE) are growing as a popular choice for the analysis of data arising from CRTs. In the past, research has shown that analyses using GEE could result in liberal inference due to the use of the empirical sandwich covariance matrix estimator, which can yield negatively biased standard error estimates when the number of clusters is not large...
January 27, 2017: Biometrical Journal. Biometrische Zeitschrift
Jeremias Leão, Víctor Leiva, Helton Saulo, Vera Tomazella
In survival models, some covariates affecting the lifetime could not be observed or measured. These covariates may correspond to environmental or genetic factors and be considered as a random effect related to a frailty of the individuals explaining their survival times. We propose a methodology based on a Birnbaum-Saunders frailty regression model, which can be applied to censored or uncensored data. Maximum-likelihood methods are used to estimate the model parameters and to derive local influence techniques...
January 5, 2017: Biometrical Journal. Biometrische Zeitschrift
Jianan Peng, Wei Liu, Frank Bretz, Ziv Shkedy
Benjamini and Yekutieli () introduced the concept of the false coverage-statement rate (FCR) to account for selection when the confidence intervals (CIs) are constructed only for the selected parameters. Dose-response analysis in dose-response microarray experiments is conducted only for genes having monotone dose-response relationship, which is a selection problem. In this paper, we consider multiple CIs for the mean gene expression difference between the highest dose and control in monotone dose-response microarray experiments for selected parameters adjusted for the FCR...
December 26, 2016: Biometrical Journal. Biometrische Zeitschrift
Nathaniel E Helwig
Longitudinal data are inherently multimode in the sense that such data are often collected across multiple modes of variation, for example, time × variables × subjects. In many longitudinal studies, multiple variables are collected to measure some latent construct(s) of interest. In such cases, the goal is to understand temporal trends in the latent variables, as well as individual differences in the trends. Multimode component analysis models provide a powerful framework for discovering latent trends in longitudinal data...
December 26, 2016: Biometrical Journal. Biometrische Zeitschrift
(no author information available yet)
No abstract text is available yet for this article.
March 2017: Biometrical Journal. Biometrische Zeitschrift
Karl Wegscheider, Tim Friede
Confidentiality and informed consent are important concepts enabling the sharing of sensitive data. In a paper on this topic of this issue, Williams and Pigeot () discuss that these have to be balanced with openness to ensure research standards. In this opinion paper, we give some background on how the paper by Williams and Pigeot evolved, reflect on their concepts, and provide some examples of the application of these concepts in various settings relevant to biostatisticians working in health research.
March 2017: Biometrical Journal. Biometrische Zeitschrift
Marco Alfó, Dankmar Böhning
No abstract text is available yet for this article.
March 2017: Biometrical Journal. Biometrische Zeitschrift
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