Sequential monitoring for comparison of changes in a response variable in clinical studies.

abstract：:Statistical methods for the detection of genes influencing quantitative traits with the aid of genetic markers are well developed for normally distributed, fully observed phenotypes. Many experiments are concerned with failure-time phenotypes, which have skewed distributions and which are usually subject to censoring ...

journal_title：Biometrics

authors： Diao G,Lin DY

更新日期：2005-09-01 00:00:00

abstract：:We propose a Bayesian latent Ornstein-Uhlenbeck (OU) model to analyze unbalanced longitudinal data of binary and ordinal variables, which are manifestations of fewer continuous latent variables. We focus on the evolution of such latent variables when they continuously change over time. Existing approaches are limited ...

journal_title：Biometrics

authors： Tran TD,Lesaffre E,Verbeke G,Duyck J

更新日期：2020-05-11 00:00:00

abstract：:In this paper we consider the use of within-subject coefficient of variation (WCV) for assessing the reproducibility or reliability of a measurement. Application to assessing reproducibility of biochemical markers for measuring bone turnover is described and the comparison with intraclass correlation is discussed. Bot...

journal_title：Biometrics

authors： Quan H,Shih WJ

更新日期：1996-12-01 00:00:00

abstract：:Recurrent events data are commonly encountered in medical studies. In many applications, only the number of events during the follow-up period rather than the recurrent event times is available. Two important challenges arise in such studies: (a) a substantial portion of subjects may not experience the event, and (b) ...

journal_title：Biometrics

authors： Diao G,Zeng D,Hu K,Ibrahim JG

更新日期：2019-12-01 00:00:00

abstract：:When testing the null hypothesis that treatment arm-specific survival-time distributions are equal, the log-rank test is asymptotically valid when the distribution of time to censoring is conditionally independent of randomized treatment group given survival time. We introduce a test of the null hypothesis for use whe...

journal_title：Biometrics

authors： DiRienzo AG

更新日期：2003-09-01 00:00:00

abstract：:This article develops a latent model and likelihood-based inference to detect temporal clustering of events. The model mimics typical processes generating the observed data. We apply model selection techniques to determine the number of clusters, and develop likelihood inference and a Monte Carlo expectation-maximizat...

journal_title：Biometrics

authors： Xie M,Sun Q,Naus J

更新日期：2009-12-01 00:00:00

abstract：:A class of adaptive weighted log-rank statistics is described where the vector of weights is chosen in a data-dependent way from a family of "smooth" weight vectors. A parametric family of weight vectors is identified which includes most shapes of weighting vectors that will be near optimal in many cancer prevention a...

journal_title：Biometrics

authors： Self SG

更新日期：1991-09-01 00:00:00

abstract：:In this article, we study nonparametric estimation of the mean function of a counting process with panel observations. We introduce the gamma frailty variable to account for the intracorrelation between the panel counts of the counting process and construct a maximum pseudo-likelihood estimate with the frailty variabl...

journal_title：Biometrics

authors： Zhang Y,Jamshidian M

更新日期：2003-12-01 00:00:00

abstract：:The data set presented relates a binomial response to ordered levels of an explanatory variable, representing doses of a drug, with data collected at several centers. A study goal is to test independence of the response and the ordinal factor, assuming under the alternative only that the binomial parameter is a monoto...

journal_title：Biometrics

authors： Agresti A,Coull BA

更新日期：1996-09-01 00:00:00

abstract：:In controlled clinical trials there are usually several prognostic factors known or thought to influence the patient's ability to respond to treatment. Therefore, the method of sequential treatment assignment needs to be designed so that treatment balance is simultaneously achieved across all such patients factor. Tra...

journal_title：Biometrics

authors： Pocock SJ,Simon R

更新日期：1975-03-01 00:00:00

abstract：:Case-control studies offer a rapid and efficient way to evaluate hypotheses. On the other hand, proper selection of the controls is challenging, and the potential for selection bias is a major weakness. Valid inferences about parameters of interest cannot be drawn if selection bias exists. Furthermore, the selection b...

journal_title：Biometrics

authors： Lin IF,Paik MC

更新日期：2001-12-01 00:00:00

abstract：:In this article, we demonstrate a statistical method for fitting the parameters of a sophisticated network and epidemic model to disease data. The pattern of contacts between hosts is described by a class of dyadic independence exponential-family random graph models (ERGMs), whereas the transmission process that runs ...

journal_title：Biometrics

authors： Groendyke C,Welch D,Hunter DR

更新日期：2012-09-01 00:00:00

abstract：:An important objective in biomedical and environmental risk assessment is estimation of minimum exposure levels that induce a pre-specified adverse response in a target population. The exposure points in such settings are typically referred to as benchmark doses (BMDs). Parametric Bayesian estimation for finding BMDs ...

journal_title：Biometrics

authors： Fang Q,Piegorsch WW,Simmons SJ,Li X,Chen C,Wang Y

更新日期：2015-12-01 00:00:00

abstract：:Spatial data have become increasingly common in epidemiology and public health research thanks to advances in GIS (Geographic Information Systems) technology. In health research, for example, it is common for epidemiologists to incorporate geographically indexed data into their studies. In practice, however, the spati...

journal_title：Biometrics

authors： Huque MH,Bondell HD,Carroll RJ,Ryan LM

更新日期：2016-09-01 00:00:00

abstract：:We describe a simple, computationally efficient, permutation-based procedure for selecting the penalty parameter in LASSO-penalized regression. The procedure, permutation selection, is intended for applications where variable selection is the primary focus, and can be applied in a variety of structural settings, inclu...

journal_title：Biometrics

authors： Sabourin JA,Valdar W,Nobel AB

更新日期：2015-12-01 00:00:00

abstract：:Differential equations are extensively used for modeling dynamics of physical processes in many scientific fields such as engineering, physics, and biomedical sciences. Parameter estimation of differential equation models is a challenging problem because of high computational cost and high-dimensional parameter space....

journal_title：Biometrics

authors： Wu H,Xue H,Kumar A

更新日期：2012-06-01 00:00:00

abstract：:This article proposes an efficient approach to screening genes associated with a phenotypic variable of interest in genomic studies with subgroups. In order to capture and detect various association profiles across subgroups, we flexibly estimate the underlying effect size distribution across subgroups using a semi-pa...

journal_title：Biometrics

authors： Matsui S,Noma H,Qu P,Sakai Y,Matsui K,Heuck C,Crowley J

更新日期：2018-03-01 00:00:00

abstract：:Ophthalmologic studies often compare several groups of subjects for the presence or absence of some ocular finding, where each subject may contribute two eyes to the analysis, the values from the two eyes being highly correlated. Rosner (1982, Biometrics 38, 105-114) and Dallal (1988, Biometrics 44, 253-257) proposed ...

journal_title：Biometrics

authors： Donner A

更新日期：1989-06-01 00:00:00

abstract：:We consider a semiparametric inference procedure for data from epidemiologic studies conducted with a two-component sampling scheme where both a simple random sample and multiple outcome- or outcome-/auxiliary-dependent samples are observed. This sampling scheme allows the investigators to oversample certain subpopula...

journal_title：Biometrics

authors： Wang X,Zhou H

更新日期：2006-12-01 00:00:00

abstract：:The characteristics of deleterious genes have been of great interest in both theory and practice in genetics. Because of the complex genetic mechanism of these deleterious genes, most current studies try to estimate the overall magnitude of mortality effects on a population, which is characterized classically by the n...

journal_title：Biometrics

authors： Lee JK,Lascoux M,Newton MA,Nordheim EV

更新日期：1999-06-01 00:00:00

abstract：:We consider the problem of estimating a population size from successive catches taken during a removal experiment and propose two estimating functions approaches, the traditional quasi-likelihood (TQL) approach for dependent observations and the conditional quasi-likelihood (CQL) approach using the conditional mean an...

journal_title：Biometrics

authors： Wang YG

更新日期：1999-12-01 00:00:00

abstract：:R. A. Fisher is widely respected for his contributions to both statistics and genetics. For instance, his 1930 text on The Genetical Theory of Natural Selection remains a watershed contribution in that area. Fisher's subsequent research led him to study the work of (Johann) Gregor Mendel, the 19th century monk who fir...

journal_title：Biometrics

authors： Piegorsch WW

更新日期：1990-12-01 00:00:00

abstract：SUMMARY:Recently, median regression models have received increasing attention. When continuous responses follow a distribution that is quite different from a normal distribution, usual mean regression models may fail to produce efficient estimators whereas median regression models may perform satisfactorily. In this ar...

journal_title：Biometrics

authors： Yi GY,He W

更新日期：2009-06-01 00:00:00

abstract：:We investigate two-stage parametric and two-stage semi-parametric estimation procedures for the association parameter in copula models for bivariate survival data where censoring in either or both components is allowed. We derive asymptotic properties of the estimators and compare their performance by simulations. Bot...

journal_title：Biometrics

authors： Shih JH,Louis TA

更新日期：1995-12-01 00:00:00

abstract：:Moment-based methods for analyzing repeated binary responses using the marginal odds ratio as a measure of association have been proposed by a number of authors. Carey, Zeger, and Diggle (1993, Biometrika 80, 517-526) have recently described how the marginal odds ratio can be estimated using generalized estimating equ...

journal_title：Biometrics

authors： Lipsitz SR,Fitzmaurice GM

更新日期：1996-09-01 00:00:00

abstract：:Vaccine-induced protection may not be homogeneous across individuals. It is possible that a vaccine gives complete protection for a portion of individuals, while the rest acquire only incomplete (leaky) protection of varying magnitude. If vaccine efficacy is estimated under wrong assumptions about such individual leve...

journal_title：Biometrics

authors： Mehtälä J,Dagan R,Auranen K

更新日期：2016-09-01 00:00:00

abstract：:This paper presents the development, application and evaluation of a stochastic model of the frequency of occurrence of transient ischemic attacks (TIAs). TIAs occur during periods of abnormal arterial activity. The TIAs which occur during a single period of abnormal activity are called a cluster of TIAs. Thus, the nu...

journal_title：Biometrics

authors： Dunn JK,Hardy RJ

更新日期：1980-03-01 00:00:00

abstract：:Andersen et al. (1985, Biometrics 41, 921-932) gave an estimator of the cumulative relative mortality comparing rates of death in an epidemiologic cohort to an external population as a function of time when covariate information is available on all cohort members. We present an analogous estimator when covariate infor...

journal_title：Biometrics

authors： Borgan O,Langholz B

更新日期：1993-06-01 00:00:00

abstract：:Procedures for estimating the genetic parameters of plant populations frequently employ progeny testing to ascertain the genotype of maternal plants. However, when experimental resources are limited (e.g., electrophoretic markers), the large progeny sizes required for accurate typing severely restricts the numbers of ...

journal_title：Biometrics

authors： Brown AH

更新日期：1975-03-01 00:00:00

abstract：:We suggest an estimator for the proportional odds cumulative incidence model for competing risks data. The key advantage of this model is that the regression parameters have the simple and useful odds ratio interpretation. The model has been considered by many authors, but it is rarely used in practice due to the lack...

journal_title：Biometrics

authors： Eriksson F,Li J,Scheike T,Zhang MJ

更新日期：2015-09-01 00:00:00