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Biometrical Journal. Biometrische Zeitschrift

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https://www.readbyqxmd.com/read/28699334/characterizing-cross-subject-spatial-interaction-patterns-in-functional-magnetic-resonance-imaging-studies-a-two-stage-point-process-model
#1
Adél Lee, Aila Särkkä, Tara M Madhyastha, Thomas J Grabowski
We develop a two-stage spatial point process model that introduces new characterizations of activation patterns in multisubject functional Magnetic Resonance Imaging (fMRI) studies. Conventionally multisubject fMRI methods rely on combining information across subjects one voxel at a time in order to identify locations of peak activation in the brain. The two-stage model that we develop here addresses shortcomings of standard methods by explicitly modeling the spatial structure of functional signals and recognizing that corresponding cross-subject functional signals can be spatially misaligned...
July 12, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28692782/a-comparison-of-bivariate-multivariate-random-effects-and-poisson-correlated-gamma-frailty-models-to-meta-analyze-individual-patient-data-of-ordinal-scale-diagnostic-tests
#2
Gabrielle Simoneau, Brooke Levis, Pim Cuijpers, John P A Ioannidis, Scott B Patten, Ian Shrier, Charles H Bombardier, Flavia de Lima Osório, Jesse R Fann, Dwenda Gjerdingen, Femke Lamers, Manote Lotrakul, Bernd Löwe, Juwita Shaaban, Lesley Stafford, Henk C P M van Weert, Mary A Whooley, Karin A Wittkampf, Albert S Yeung, Brett D Thombs, Andrea Benedetti
Individual patient data (IPD) meta-analyses are increasingly common in the literature. In the context of estimating the diagnostic accuracy of ordinal or semi-continuous scale tests, sensitivity and specificity are often reported for a given threshold or a small set of thresholds, and a meta-analysis is conducted via a bivariate approach to account for their correlation. When IPD are available, sensitivity and specificity can be pooled for every possible threshold. Our objective was to compare the bivariate approach, which can be applied separately at every threshold, to two multivariate methods: the ordinal multivariate random-effects model and the Poisson correlated gamma-frailty model...
July 10, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28692751/multilevel-covariance-regression-with-correlated-random-effects-in-the-mean-and-variance-structure
#3
Adrian Quintero, Emmanuel Lesaffre
Multivariate regression methods generally assume a constant covariance matrix for the observations. In case a heteroscedastic model is needed, the parametric and nonparametric covariance regression approaches can be restrictive in the literature. We propose a multilevel regression model for the mean and covariance structure, including random intercepts in both components and allowing for correlation between them. The implied conditional covariance function can be different across clusters as a result of the random effect in the variance structure...
July 10, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28692743/a-flexible-multivariate-random-effects-proportional-odds-model-with-application-to-adverse-effects-during-radiation-therapy
#4
Nicole H Augustin, Sung Won Kim, Annemarie Uhlig, Christina Hanser, Michael Henke, Martin Schumacher
Radiation therapy in patients with head and neck cancer has a toxic effect on mucosa, the soft tissue in and around the mouth. Hence mucositis is a serious common side effect and is a condition characterized by pain and inflammation of the surface of the mucosa. Although the mucosa recovers during breaks of and following the radiotherapy course, the recovery will depend on the type of tissue involved and on its location. We present a novel flexible multivariate random effects proportional odds model that takes account of the longitudinal course of oral mucositis at different mouth sites and of the radiation dosage (in terms of cumulative dose)...
July 10, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28664629/mixture-model-with-multiple-allocations-for-clustering-spatially-correlated-observations-in-the-analysis-of-chip-seq-data
#5
Saverio Ranciati, Cinzia Viroli, Ernst C Wit
Model-based clustering is a technique widely used to group a collection of units into mutually exclusive groups. There are, however, situations in which an observation could in principle belong to more than one cluster. In the context of next-generation sequencing (NGS) experiments, for example, the signal observed in the data might be produced by two (or more) different biological processes operating together and a gene could participate in both (or all) of them. We propose a novel approach to cluster NGS discrete data, coming from a ChIP-Seq experiment, with a mixture model, allowing each unit to belong potentially to more than one group: these multiple allocation clusters can be flexibly defined via a function combining the features of the original groups without introducing new parameters...
June 30, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28660685/studying-the-relationship-between-a-woman-s-reproductive-lifespan-and-age-at-menarche-using-a-bayesian-multivariate-structured-additive-distributional-regression-model
#6
Elisa Duarte, Bruno de Sousa, Carmen Cadarso-Suárez, Nadja Klein, Thomas Kneib, Vítor Rodrigues
Studies addressing breast cancer risk factors have been looking at trends relative to age at menarche and menopause. These studies point to a downward trend of age at menarche and an upward trend for age at menopause, meaning an increase of a woman's reproductive lifespan cycle. In addition to studying the effect of the year of birth on the expectation of age at menarche and a woman's reproductive lifespan, it is important to understand how a woman's cohort affects the correlation between these two variables...
June 29, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28660641/author-response-to-the-contributors-to-the-discussion-on-a-critical-evaluation-of-the-current-p-value-controversy
#7
Stefan Wellek
No abstract text is available yet for this article.
June 29, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28626952/multivariate-binary-classification-of-imbalanced-datasets-a-case-study-based-on-high-dimensional-multiplex-autoimmune-assay-data
#8
Laura Schlieker, Anna Telaar, Angelika Lueking, Peter Schulz-Knappe, Carmen Theek, Katja Ickstadt
The classification of a population by a specific trait is a major task in medicine, for example when in a diagnostic setting groups of patients with specific diseases are identified, but also when in predictive medicine a group of patients is classified into specific disease severity classes that might profit from different treatments. When the sizes of those subgroups become small, for example in rare diseases, imbalances between the classes are more the rule than the exception and make statistical classification problematic when the error rate of the minority class is high...
June 19, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28620935/fast-precision-estimation-in-high-dimensional-multivariate-joint-models
#9
Vahid Nassiri, Anna Ivanova, Geert Molenberghs, Geert Verbeke
A fast way is proposed based on the multiple outputation idea (Hoffman et al., ; Follmann et al., ) to calculate the precision of parameter estimates for high-dimensional multivariate joint models using a pairwise approach (Fieuws and Verbeke, ; Fieuws et al., ). Simulation results as well as data analysis shows possibly more than 2500 times faster computations using the proposed method. In our real data illustration, the time gain is more than 330 times.
June 16, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28605047/stratified-exact-tests-for-the-weak-causal-null-hypothesis-in-randomized-trials-with-a-binary-outcome
#10
Yasutaka Chiba
Fisher's exact test is commonly used to compare two groups when the outcome is binary in randomized trials. In the context of causal inference, this test explores the sharp causal null hypothesis (i.e. the causal effect of treatment is the same for all subjects), but not the weak causal null hypothesis (i.e. the causal risks are the same in the two groups). Therefore, in general, rejection of the null hypothesis by Fisher's exact test does not mean that the causal risk difference is not zero. Recently, Chiba (Journal of Biometrics and Biostatistics 2015; 6: 244) developed a new exact test for the weak causal null hypothesis when the outcome is binary in randomized trials; the new test is not based on any large sample theory and does not require any assumption...
June 12, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28593719/penalized-estimation-in-latent-markov-models-with-application-to-monitoring-serum-calcium-levels-in-end-stage-kidney-insufficiency
#11
Alessio Farcomeni
We introduce a penalized likelihood form for latent Markov models. We motivate its use for biomedical applications where the sample size is in the order of the tens, or at most hundreds, and there are only few repeated measures. The resulting estimates never break down, while spurious solutions are often obtained by maximizing the likelihood itself. We discuss model choice based on the Takeuchi Information Criterion. Simulations and a real-data application to monitoring serum Calcium levels in end-stage kidney disease are used for illustration...
June 8, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28547927/contribution-to-the-discussion-of-a-critical-evaluation-of-the-current-p-value-controversy
#12
Fulvio De Santis
No abstract text is available yet for this article.
May 26, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28547812/contribution-to-the-discussion-of-a-critical-evaluation-of-the-current-p-value-controversy
#13
Werner Brannath
No abstract text is available yet for this article.
May 26, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28543300/an-objective-bayes-perspective-on-p-values
#14
Leonhard Held
No abstract text is available yet for this article.
May 24, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28508545/comparison-of-joint-modeling-and-landmarking-for-dynamic-prediction-under-an-illness-death-model
#15
Krithika Suresh, Jeremy M G Taylor, Daniel E Spratt, Stephanie Daignault, Alexander Tsodikov
Dynamic prediction incorporates time-dependent marker information accrued during follow-up to improve personalized survival prediction probabilities. At any follow-up, or "landmark", time, the residual time distribution for an individual, conditional on their updated marker values, can be used to produce a dynamic prediction. To satisfy a consistency condition that links dynamic predictions at different time points, the residual time distribution must follow from a prediction function that models the joint distribution of the marker process and time to failure, such as a joint model...
May 16, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28508431/a-spatially-balanced-design-with-probability-function-proportional-to-the-within-sample-distance
#16
Roberto Benedetti, Federica Piersimoni
The units observed in a biological, agricultural, and environmental survey are often randomly selected from a finite population whose main feature is to be geo-referenced thus its spatial distribution should be used as essential information in designing the sample. In particular our interest is focused on probability samples that are well spread over the population in every dimension which in recent literature are defined as spatially balanced samples. To approach the problem we used the within sample distance as the summary index of the spatial distribution of a random selection criterion...
May 16, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28504870/a-critical-evaluation-of-the-current-p-value-controversy
#17
REVIEW
Stefan Wellek
This article has been triggered by the initiative launched in March 2016 by the Board of Directors of the American Statistical Association (ASA) to counteract the current p-value focus of statistical research practices that allegedly "have contributed to a reproducibility crisis in science." It is pointed out that in the very wide field of statistics applied to medicine, many of the problems raised in the ASA statement are not as severe as in the areas the authors may have primarily in mind, although several of them are well-known experts in biostatistics and epidemiology...
May 15, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28503762/contribution-to-the-discussion-of-a-critical-evaluation-of-the-current-p-value-controversy
#18
Mauro Gasparini
No abstract text is available yet for this article.
May 15, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28480583/editorial-for-the-special-topic-on-multiple-comparison-procedures
#19
Ajit C Tamhane
No abstract text is available yet for this article.
May 8, 2017: Biometrical Journal. Biometrische Zeitschrift
https://www.readbyqxmd.com/read/28471053/contribution-to-the-discussion-of-the-paper-by-stefan-wellek-a-critical-evaluation-of-the-current-p-value-controversy
#20
Alessio Farcomeni
No abstract text is available yet for this article.
May 4, 2017: Biometrical Journal. Biometrische Zeitschrift
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