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International Journal of Biostatistics

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https://www.readbyqxmd.com/read/30471221/optimal-and-or-efficient-two-treatment-crossover-designs-for-five-carryover-models
#1
Jigneshkumar Gondaliya, Jyoti Divecha
Crossover designs robust to changes in carryover models are useful in clinical trials where the nature of carryover effects is not known in advance. The designs have been characterized for being optimal and efficient under no carryover-, traditional-, and, self and mixed carryover- models, however, ignoring the number of subjects, which has significant impact on both optimality and administrative convenience. In this article, adding two more practical models, the traditional, and, self and mixed carryover models having carryover effect only for the new or test treatment, a 5M algorithm is presented...
November 24, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/30465718/a-serious-flaw-in-nutrition-epidemiology-a-meta-analysis-study
#2
Karl E Peace, JingJing Yin, Haresh Rochani, Sarbesh Pandeya, Stanley Young
Background Many researchers have studied the relationship between diet and health. Specifically, there are papers showing an association between the consumption of sugar sweetened beverages and Type 2 diabetes. Many meta-analyses use individual studies that do not attempt to adjust for multiple testing or multiple modeling. Hence the claims reported in a meta-analysis paper may be unreliable as the base papers do not ensure unbiased statistics. Objective Determine (i) the statistical reliability of 10 papers and (ii) indirectly the reliability of the meta-analysis study...
November 22, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/30379638/maximum-likelihood-estimation-in-a-semicontinuous-survival-model-with-covariates-subject-to-detection-limits
#3
Paul W Bernhardt
Semicontinuous data are common in biological studies, occurring when a variable is continuous over a region but has a point mass at one or more points. In the motivating Genetic and Inflammatory Markers of Sepsis (GenIMS) study, it was of interest to determine how several biomarkers subject to detection limits were related to survival for patients entering the hospital with community acquired pneumonia. While survival times were recorded for all individuals in the study, the primary endpoint of interest was the binary event of 90-day survival, and no patients were lost to follow-up prior to 90 days...
October 31, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/30173203/estimating-causal-effects-from-nonparanormal-observational-data
#4
Seyed Mahdi Mahmoudi, Ernst C Wit
No abstract text is available yet for this article.
September 1, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/30048236/a-truncation-model-for-estimating-species-richness
#5
Babagnidé François Koladjo, Mesrob I Ohannessian, Elisabeth Gassiat
We propose a truncation model for the abundance distribution in species richness estimation. This model is inherently semiparametric and incorporates an unknown truncation threshold between rare and abundant observations. Using the conditional likelihood, we derive a class of estimators for the parameters in this model by stepwise maximization. The species richness estimator is given by the integer maximizing the binomial likelihood, given all other parameters in the model. Under regularity conditions, we show that our estimators of the model parameters are asymptotically efficient...
July 26, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/30024852/a-new-class-of-robust-two-sample-wald-type-tests
#6
Abhik Ghosh, Nirian Martin, Ayanendranath Basu, Leandro Pardo
Parametric hypothesis testing associated with two independent samples arises frequently in several applications in biology, medical sciences, epidemiology, reliability and many more. In this paper, we propose robust Wald-type tests for testing such two sample problems using the minimum density power divergence estimators of the underlying parameters. In particular, we consider the simple two-sample hypothesis concerning the full parametric homogeneity as well as the general two-sample (composite) hypotheses involving some nuisance parameters...
July 19, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/29981281/a-spatio-temporal-model-and-inference-tools-for-longitudinal-count-data-on-multicolor-cell-growth
#7
PuXue Qiao, Christina Mølck, Davide Ferrari, Frédéric Hollande
Multicolor cell spatio-temporal image data have become important to investigate organ development and regeneration, malignant growth or immune responses by tracking different cell types both in vivo and in vitro. Statistical modeling of image data from common longitudinal cell experiments poses significant challenges due to the presence of complex spatio-temporal interactions between different cell types and difficulties related to measurement of single cell trajectories. Current analysis methods focus mainly on univariate cases, often not considering the spatio-temporal effects affecting cell growth between different cell populations...
July 7, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/29906269/a-fast-and-robust-way-to-estimate-overlap-of-niches-and-draw-inference
#8
Judith H Parkinson, Raoul Kutil, Jonas Kuppler, Robert R Junker, Wolfgang Trutschnig, Arne C Bathke
The problem of quantifying the overlap of Hutchinsonian niches has received much attention lately, in particular in quantitative ecology, from where it also originates. However, the niche concept has the potential to also be useful in many other application areas, as for example in economics. We are presenting a fully nonparametric, robust solution to this problem, along with exact shortcut formulas based on rank-statistics, and with a rather intuitive probabilistic interpretation. Furthermore, by deriving the asymptotic sampling distribution of the estimators, we are proposing the first asymptotically valid inference method, providing confidence intervals for the niche overlap...
June 15, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/29883322/marginal-structural-models-with-counterfactual-effect-modifiers
#9
Wenjing Zheng, Zhehui Luo, Mark J van der Laan
In health and social sciences, research questions often involve systematic assessment of the modification of treatment causal effect by patient characteristics. In longitudinal settings, time-varying or post-intervention effect modifiers are also of interest. In this work, we investigate the robust and efficient estimation of the Counterfactual-History-Adjusted Marginal Structural Model (van der Laan MJ, Petersen M. Statistical learning of origin-specific statically optimal individualized treatment rules. Int J Biostat...
June 8, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/29878883/unfolding-the-genome-the-case-study-of-p-falciparum
#10
Nelle Varoquaux
The development of new ways to probe samples for the three-dimensional (3D) structure of DNA paves the way for in depth and systematic analyses of the genome architecture. 3C-like methods coupled with high-throughput sequencing can now assess physical interactions between pairs of loci in a genome-wide fashion, thus enabling the creation of genome-by-genome contact maps. The spreading of such protocols creates many new opportunities for methodological development: how can we infer 3D models from these contact maps? Can such models help us gain insights into biological processes? Several recent studies applied such protocols to P...
June 7, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/29676993/nonparametric-interval-estimators-for-the-coefficient-of-variation
#11
Dongliang Wang, Margaret K Formica, Song Liu
The coefficient of variation (CV) is a widely used scaleless measure of variability in many disciplines. However the inference for the CV is limited to parametric methods or standard bootstrap. In this paper we propose two nonparametric methods aiming to construct confidence intervals for the coefficient of variation. The first one is to apply the empirical likelihood after transforming the original data. The second one is a modified jackknife empirical likelihood method. We also propose bootstrap procedures for calibrating the test statistics...
April 19, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/29621006/a-bayesian-framework-for-estimating-the-concordance-correlation-coefficient-using-skew-elliptical-distributions
#12
Dai Feng, Richard Baumgartner, Vladimir Svetnik
The concordance correlation coefficient (CCC) is a widely used scaled index in the study of agreement. In this article, we propose estimating the CCC by a unified Bayesian framework that can (1) accommodate symmetric or asymmetric and light- or heavy-tailed data; (2) select model from several candidates; and (3) address other issues frequently encountered in practice such as confounding covariates and missing data. The performance of the proposal was studied and demonstrated using simulated as well as real-life biomarker data from a clinical study of an insomnia drug...
April 5, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/29517976/notes-on-test-and-estimation-in-comparison-of-three-treatments-under-a-simple-carry-over-three-period-model
#13
Kung-Jong Lui
Under the three-treatment three-period crossover design with simple carry-over effects, we derive the least-squares estimators for period effects, treatment effects and carry-over effects, as well as their covariance matrix in closed and explicit expressions. Using Monte Carlo simulation, we compare the test procedure adjusting carry-over with that ignoring carry-over with respect to Type I error and power. We further compare interval estimators adjusting carry-over with those ignoring carry-over with respect to the coverage probability and the average length...
March 7, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/29389664/joint-models-of-longitudinal-and-time-to-event-data-with-more-than-one-event-time-outcome-a-review
#14
Graeme L Hickey, Pete Philipson, Andrea Jorgensen, Ruwanthi Kolamunnage-Dona
Methodological development and clinical application of joint models of longitudinal and time-to-event outcomes have grown substantially over the past two decades. However, much of this research has concentrated on a single longitudinal outcome and a single event time outcome. In clinical and public health research, patients who are followed up over time may often experience multiple, recurrent, or a succession of clinical events. Models that utilise such multivariate event time outcomes are quite valuable in clinical decision-making...
January 31, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/29306919/zero-inflated-conway-maxwell-poisson-distribution-to-analyze-discrete-data
#15
Shin Zhu Sim, Ramesh C Gupta, Seng Huat Ong
In this paper, we study the zero-inflated Conway-Maxwell Poisson (ZICMP) distribution and develop a regression model. Score and likelihood ratio tests are also implemented for testing the inflation/deflation parameter. Simulation studies are carried out to examine the performance of these tests. A data example is presented to illustrate the concepts. In this example, the proposed model is compared to the well-known zero-inflated Poisson (ZIP) and the zero- inflated generalized Poisson (ZIGP) regression models...
January 9, 2018: International Journal of Biostatistics
https://www.readbyqxmd.com/read/29023235/a-generally-efficient-targeted-minimum-loss-based-estimator-based-on-the-highly-adaptive-lasso
#16
Mark van der Laan
Suppose we observe n $n$ independent and identically distributed observations of a finite dimensional bounded random variable. This article is concerned with the construction of an efficient targeted minimum loss-based estimator (TMLE) of a pathwise differentiable target parameter of the data distribution based on a realistic statistical model. The only smoothness condition we will enforce on the statistical model is that the nuisance parameters of the data distribution that are needed to evaluate the canonical gradient of the pathwise derivative of the target parameter are multivariate real valued cadlag functions (right-continuous and left-hand limits, (G...
October 12, 2017: International Journal of Biostatistics
https://www.readbyqxmd.com/read/28961139/adaptation-of-chain-event-graphs-for-use-with-case-control-studies-in-epidemiology
#17
Claire Keeble, Peter Adam Thwaites, Stuart Barber, Graham Richard Law, Paul David Baxter
Case-control studies are used in epidemiology to try to uncover the causes of diseases, but are a retrospective study design known to suffer from non-participation and recall bias, which may explain their decreased popularity in recent years. Traditional analyses report usually only the odds ratio for given exposures and the binary disease status. Chain event graphs are a graphical representation of a statistical model derived from event trees which have been developed in artificial intelligence and statistics, and only recently introduced to the epidemiology literature...
September 26, 2017: International Journal of Biostatistics
https://www.readbyqxmd.com/read/28953454/a-comparison-of-methods-for-estimating-the-determinant-of-high-dimensional-covariance-matrix
#18
COMPARATIVE STUDY
Zongliang Hu, Kai Dong, Wenlin Dai, Tiejun Tong
The determinant of the covariance matrix for high-dimensional data plays an important role in statistical inference and decision. It has many real applications including statistical tests and information theory. Due to the statistical and computational challenges with high dimensionality, little work has been proposed in the literature for estimating the determinant of high-dimensional covariance matrix. In this paper, we estimate the determinant of the covariance matrix using some recent proposals for estimating high-dimensional covariance matrix...
September 21, 2017: International Journal of Biostatistics
https://www.readbyqxmd.com/read/28930628/estimation-and-inference-for-the-mediation-proportion
#19
Daniel Nevo, Xiaomei Liao, Donna Spiegelman
In epidemiology, public health and social science, mediation analysis is often undertaken to investigate the extent to which the effect of a risk factor on an outcome of interest is mediated by other covariates. A pivotal quantity of interest in such an analysis is the mediation proportion. A common method for estimating it, termed the "difference method", compares estimates from models with and without the hypothesized mediator. However, rigorous methodology for estimation and statistical inference for this quantity has not previously been available...
September 20, 2017: International Journal of Biostatistics
https://www.readbyqxmd.com/read/28686573/modelling-mixed-types-of-outcomes-in-additive-genetic-models
#20
Wagner Hugo Bonat
We present a general statistical modelling framework for handling multivariate mixed types of outcomes in the context of quantitative genetic analysis. The models are based on the multivariate covariance generalized linear models, where the matrix linear predictor is composed of an identity matrix combined with a relatedness matrix defined by a pedigree, representing the environmental and genetic components, respectively. We also propose a new index of heritability for non-Gaussian data. A case study on house sparrow (Passer domesticus) population with continuous, binomial and count outcomes is employed to motivate the new model...
July 7, 2017: International Journal of Biostatistics
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