International Journal of Biostatistics最新文献_第10页

The area under the generalized receiver-operating characteristic curve. 广义接收机工作特性曲线下的面积。

IF 1.2 4区数学

International Journal of Biostatistics Pub Date : 2021-03-24 DOI: 10.1515/ijb-2020-0091

Pablo Martínez-Camblor, Sonia Pérez-Fernández, Susana Díaz-Coto

{"title":"The area under the generalized receiver-operating characteristic curve.","authors":"Pablo Martínez-Camblor, Sonia Pérez-Fernández, Susana Díaz-Coto","doi":"10.1515/ijb-2020-0091","DOIUrl":"https://doi.org/10.1515/ijb-2020-0091","url":null,"abstract":"The receiver operating-characteristic (ROC) curve is a well-known graphical tool routinely used for evaluating the discriminatory ability of continuous markers, referring to a binary characteristic. The area under the curve (AUC) has been proposed as a summarized accuracy index. Higher values of the marker are usually associated with higher probabilities of having the characteristic under study. However, there are other situations where both, higher and lower marker scores, are associated with a positive result. The generalized ROC (gROC) curve has been proposed as a proper extension of the ROC curve to fit these situations. Of course, the corresponding area under the gROC curve, gAUC, has also been introduced as a global measure of the classification capacity. In this paper, we study in deep the gAUC properties. The weak convergence of its empirical estimator is provided while deriving an explicit and useful expression for the asymptotic variance. We also obtain the expression for the asymptotic covariance of related gAUCs and propose a non-parametric procedure to compare them. The finite-samples behavior is studied through Monte Carlo simulations under different scenarios, presenting a real-world problem in order to illustrate its practical application. The R code functions implementing the procedures are provided as Supplementary Material.","PeriodicalId":50333,"journal":{"name":"International Journal of Biostatistics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2021-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1515/ijb-2020-0091","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"25512815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 10

Regularized bidimensional estimation of the hazard rate. 危险率的正则化二维估计。

IF 1.2 4区数学

International Journal of Biostatistics Pub Date : 2021-03-24 DOI: 10.1515/ijb-2019-0003

Vivien Goepp, Jean-Christophe Thalabard, Grégory Nuel, Olivier Bouaziz

{"title":"Regularized bidimensional estimation of the hazard rate.","authors":"Vivien Goepp, Jean-Christophe Thalabard, Grégory Nuel, Olivier Bouaziz","doi":"10.1515/ijb-2019-0003","DOIUrl":"https://doi.org/10.1515/ijb-2019-0003","url":null,"abstract":"In epidemiological or demographic studies, with variable age at onset, a typical quantity of interest is the incidence of a disease (for example the cancer incidence). In these studies, the individuals are usually highly heterogeneous in terms of dates of birth (the cohort) and with respect to the calendar time (the period) and appropriate estimation methods are needed. In this article a new estimation method is presented which extends classical age-period-cohort analysis by allowing interactions between age, period and cohort effects. We introduce a bidimensional regularized estimate of the hazard rate where a penalty is introduced on the likelihood of the model. This penalty can be designed either to smooth the hazard rate or to enforce consecutive values of the hazard to be equal, leading to a parsimonious representation of the hazard rate. In the latter case, we make use of an iterative penalized likelihood scheme to approximate the L0 norm, which makes the computation tractable. The method is evaluated on simulated data and applied on breast cancer survival data from the SEER program.","PeriodicalId":50333,"journal":{"name":"International Journal of Biostatistics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2021-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1515/ijb-2019-0003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"25519056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Bayesian approaches to variable selection: a comparative study from practical perspectives. 贝叶斯变量选择方法:从实践角度的比较研究。

IF 1.2 4区数学

International Journal of Biostatistics Pub Date : 2021-03-24 DOI: 10.1515/ijb-2020-0130

Zihang Lu, Wendy Lou

{"title":"Bayesian approaches to variable selection: a comparative study from practical perspectives.","authors":"Zihang Lu, Wendy Lou","doi":"10.1515/ijb-2020-0130","DOIUrl":"https://doi.org/10.1515/ijb-2020-0130","url":null,"abstract":"In many clinical studies, researchers are interested in parsimonious models that simultaneously achieve consistent variable selection and optimal prediction. The resulting parsimonious models will facilitate meaningful biological interpretation and scientific findings. Variable selection via Bayesian inference has been receiving significant advancement in recent years. Despite its increasing popularity, there is limited practical guidance for implementing these Bayesian approaches and evaluating their comparative performance in clinical datasets. In this paper, we review several commonly used Bayesian approaches to variable selection, with emphasis on application and implementation through R software. These approaches can be roughly categorized into four classes: namely the Bayesian model selection, spike-and-slab priors, shrinkage priors, and the hybrid of both. To evaluate their variable selection performance under various scenarios, we compare these four classes of approaches using real and simulated datasets. These results provide practical guidance to researchers who are interested in applying Bayesian approaches for the purpose of variable selection.","PeriodicalId":50333,"journal":{"name":"International Journal of Biostatistics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2021-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1515/ijb-2020-0130","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"25525255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 12

Integrating additional knowledge into the estimation of graphical models. 将额外的知识集成到图形模型的估计中。

IF 1.2 4区数学

International Journal of Biostatistics Pub Date : 2021-03-09 DOI: 10.1515/ijb-2020-0133

Yunqi Bu, Johannes Lederer

引用次数: 10

Power formulas for mixed effects models with random slope and intercept comparing rate of change across groups. 具有随机斜率和截距比较组间变化率的混合效应模型的功率公式。

IF 1.2 4区数学

International Journal of Biostatistics Pub Date : 2021-01-18 DOI: 10.1515/ijb-2020-0107

Yu Zhao, Steven D Edland

{"title":"Power formulas for mixed effects models with random slope and intercept comparing rate of change across groups.","authors":"Yu Zhao, Steven D Edland","doi":"10.1515/ijb-2020-0107","DOIUrl":"10.1515/ijb-2020-0107","url":null,"abstract":"We have previously derived power calculation formulas for cohort studies and clinical trials using the longitudinal mixed effects model with random slopes and intercepts to compare rate of change across groups [Ard & Edland, Power calculations for clinical trials in Alzheimer's disease. J Alzheim Dis 2011;21:369-77]. We here generalize these power formulas to accommodate 1) missing data due to study subject attrition common to longitudinal studies, 2) unequal sample size across groups, and 3) unequal variance parameters across groups. We demonstrate how these formulas can be used to power a future study even when the design of available pilot study data (i.e., number and interval between longitudinal observations) does not match the design of the planned future study. We demonstrate how differences in variance parameters across groups, typically overlooked in power calculations, can have a dramatic effect on statistical power. This is especially relevant to clinical trials, where changes over time in the treatment arm reflect background variability in progression observed in the placebo control arm plus variability in response to treatment, meaning that power calculations based only on the placebo arm covariance structure may be anticonservative. These more general power formulas are a useful resource for understanding the relative influence of these multiple factors on the efficiency of cohort studies and clinical trials, and for designing future trials under the random slopes and intercepts model.","PeriodicalId":50333,"journal":{"name":"International Journal of Biostatistics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2021-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9156336/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"25365259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Multiple scaled symmetric distributions in allometric studies. 异速生长研究中的多尺度对称分布。

IF 1.2 4区数学

International Journal of Biostatistics Pub Date : 2021-01-18 DOI: 10.1515/ijb-2020-0059

Antonio Punzo, Luca Bagnato

{"title":"Multiple scaled symmetric distributions in allometric studies.","authors":"Antonio Punzo, Luca Bagnato","doi":"10.1515/ijb-2020-0059","DOIUrl":"https://doi.org/10.1515/ijb-2020-0059","url":null,"abstract":"In allometric studies, the joint distribution of the log-transformed morphometric variables is typically symmetric and with heavy tails. Moreover, in the bivariate case, it is customary to explain the morphometric variation of these variables by fitting a convenient line, as for example the first principal component (PC). To account for all these peculiarities, we propose the use of multiple scaled symmetric (MSS) distributions. These distributions have the advantage to be directly defined in the PC space, the kind of symmetry involved is less restrictive than the commonly considered elliptical symmetry, the behavior of the tails can vary across PCs, and their first PC is less sensitive to outliers. In the family of MSS distributions, we also propose the multiple scaled shifted exponential normal distribution, equivalent of the multivariate shifted exponential normal distribution in the MSS framework. For the sake of parsimony, we also allow the parameter governing the leptokurtosis on each PC, in the considered MSS distributions, to be tied across PCs. From an inferential point of view, we describe an EM algorithm to estimate the parameters by maximum likelihood, we illustrate how to compute standard errors of the obtained estimates, and we give statistical tests and confidence intervals for the parameters. We use artificial and real allometric data to appreciate the advantages of the MSS distributions over well-known elliptically symmetric distributions and to compare the robustness of the line from our models with respect to the lines fitted by well-established robust and non-robust methods available in the literature.","PeriodicalId":50333,"journal":{"name":"International Journal of Biostatistics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2021-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1515/ijb-2020-0059","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"25487581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

Gradient boosting for linear mixed models. 线性混合模型的梯度增强。

IF 1.2 4区数学

International Journal of Biostatistics Pub Date : 2021-01-13 DOI: 10.1515/ijb-2020-0136

Colin Griesbach, Benjamin Säfken, Elisabeth Waldmann

引用次数: 8

Asymptotic properties of the two one-sided t-tests – new insights and the Schuirmann-constant 两个单侧t检验的渐近性质——新见解和Schuirmann常数

IF 1.2 4区数学

International Journal of Biostatistics Pub Date : 2021-01-08 DOI: 10.1515/IJB-2020-0057

Christian Palmes, Tobias Bluhmki, Benedikt Funke, E. Bluhmki

{"title":"Asymptotic properties of the two one-sided t-tests – new insights and the Schuirmann-constant","authors":"Christian Palmes, Tobias Bluhmki, Benedikt Funke, E. Bluhmki","doi":"10.1515/IJB-2020-0057","DOIUrl":"https://doi.org/10.1515/IJB-2020-0057","url":null,"abstract":"Abstract The two one-sided t-tests (TOST) method is the most popular statistical equivalence test with many areas of application, i.e., in the pharmaceutical industry. Proper sample size calculation is needed in order to show equivalence with a certain power. Here, the crucial problem of choosing a suitable mean-difference in TOST sample size calculations is addressed. As an alternative concept, it is assumed that the mean-difference follows an a-priori distribution. Special interest is given to the uniform and some centered triangle a-priori distributions. Using a newly developed asymptotical theory a helpful analogy principle is found: every a-priori distribution corresponds to a point mean-difference, which we call its Schuirmann-constant. This constant does not depend on the standard deviation and aims to support the investigator in finding a well-considered mean-difference for proper sample size calculations in complex data situations. In addition to the proposed concept, we demonstrate that well-known sample size approximation formulas in the literature are in fact biased and state their unbiased corrections as well. Moreover, an R package is provided for a right away application of our newly developed concepts.","PeriodicalId":50333,"journal":{"name":"International Journal of Biostatistics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2021-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1515/IJB-2020-0057","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46667419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

The method of envelopes to concisely calculate semiparametric efficient scores under parametric restrictions. 在参数限制下，采用包络法简明地计算半参数有效分数。

IF 1.2 4区数学

International Journal of Biostatistics Pub Date : 2020-12-24 DOI: 10.1515/ijb-2019-0043

Constantine E Frangakis

{"title":"The method of envelopes to concisely calculate semiparametric efficient scores under parametric restrictions.","authors":"Constantine E Frangakis","doi":"10.1515/ijb-2019-0043","DOIUrl":"https://doi.org/10.1515/ijb-2019-0043","url":null,"abstract":"When addressing semiparametric problems with parametric restrictions (assumptions on the distribution), the efficient score (ES) of a parameter is often important for generating useful estimates. However, usual derivation of ES, although conceptually simple, is often lengthy and with many steps that do not help in understanding why its final form arises. This drawback often casts onto semiparametric estimation a mantle that can turn away otherwise able doctoral students or researchers. Here we show that many ESs can be obtained as a one-step derivation after we characterize those features (envelopes) of the unrestricted problem that are constrained in the restricted problem. We demonstrate our arguments in three problems with known ES but whose usual derivations are lengthy. We show that the envelope-based derivation is dramatically explanatory and compact, needing essentially two lines where the standard approach needs 10 or more pages. This suggests that the envelope method can add useful intuition and exegesis to both teaching and research of semiparametric estimation.","PeriodicalId":50333,"journal":{"name":"International Journal of Biostatistics","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2020-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1515/ijb-2019-0043","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38995775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A kernel- and optimal transport- based test of independence between covariates and right-censored lifetimes. 基于核和最优传输的协变量和右审查寿命之间的独立性检验。

IF 1.2 4区数学

International Journal of Biostatistics Pub Date : 2020-12-02 DOI: 10.1515/ijb-2020-0022

David Rindt, Dino Sejdinovic, David Steinsaltz

引用次数: 4