Extension of the rank sum test for clustered data: two-group comparisons with group membership defined at the subunit level.

abstract：:Laska and Meisner (1989, Biometrics 45, 1139-1151) dealt with the problem of testing whether an identified treatment belonging to a set of k + 1 treatments is better than each of the other k treatments. They calculated sample size tables for k = 2 when using multiple t-tests or Wilcoxon-Mann-Whitney tests, both under ...

journal_title：Biometrics

authors： Horn M,Vollandt R,Dunnett CW

更新日期：2000-09-01 00:00:00

abstract：:A method is presented for choosing an additive constant c when transforming data x to y = log(x + c). The method preserves Type I error probability and power in ANOVA under the assumption that the x + c for some c are log-normally distributed. The method has advantages similar to those of rank transformations--namely,...

journal_title：Biometrics

authors： Berry DA

更新日期：1987-06-01 00:00:00

abstract：:Detecting changes in longitudinal data is important in medical research. However, the existence of measurement outliers can cause an unexpected increase in the false alarm rate in claiming changes. To reduce the outliers, a new method has been developed. In this scheme, two measures are initially taken and, if they ar...

journal_title：Biometrics

authors： Namgung YY,Yang MC

更新日期：1994-03-01 00:00:00

abstract：:We propose a nonparametric Bayesian approach to estimate the natural direct and indirect effects through a mediator in the setting of a continuous mediator and a binary response. Several conditional independence assumptions are introduced (with corresponding sensitivity parameters) to make these effects identifiable f...

journal_title：Biometrics

authors： Daniels MJ,Roy JA,Kim C,Hogan JW,Perri MG

更新日期：2012-12-01 00:00:00

abstract：:We propose a design strategy for single-arm clinical trials in which the goals are to find a dose of an experimental treatment satisfying both safety and efficacy requirements, treat a sufficiently large number of patients to estimate the rates of these events at the selected dose with a given reliability, and stop th...

journal_title：Biometrics

authors： Thall PF,Russell KE

更新日期：1998-03-01 00:00:00

abstract：:In this article, we present new methods to analyze data from an experiment using rodent models to investigate the role of p27, an important cell-cycle mediator, in early colon carcinogenesis. The responses modeled here are essentially functions nested within a two-stage hierarchy. Standard functional data analysis lit...

journal_title：Biometrics

authors： Baladandayuthapani V,Mallick BK,Young Hong M,Lupton JR,Turner ND,Carroll RJ

更新日期：2008-03-01 00:00:00

abstract：:In this article, we investigate clustering methods for multilevel functional data, which consist of repeated random functions observed for a large number of units (e.g., genes) at multiple subunits (e.g., bacteria types). To describe the within- and between variability induced by the hierarchical structure in the data...

journal_title：Biometrics

authors： Serban N,Jiang H

更新日期：2012-09-01 00:00:00

abstract：:Likelihood ratio tests for parameters estimated assuming normally distributed errors are examined under a variety of homoscedastic and heteroscedastic variance assumptions. It is assumed that gamma ij, the jth observation from the ith population, is distributed as N[mu(chi ij, beta i), (sigma i mu(chi ij, beta i)theta...

journal_title：Biometrics

authors： Kimura DK

更新日期：1990-09-01 00:00:00

abstract：:In this note we propose a frailty model called piecewise gamma frailty for correlated survival data with random effects having a nested structure. In frailty models, a dependence function defined as a hazard ratio of one member given the failure time of another member in a unit is determined by the distributional assu...

journal_title：Biometrics

authors： Paik MC,Tsai WY,Ottman R

更新日期：1994-12-01 00:00:00

abstract：:A nonparametric maximum likelihood procedure is given for estimating the survivor function from right-censored data. It approximates the hazard rate by a simple function such as a spline, with different approximations yielding different estimators. A special case is that proposed by Nelson (1969, Journal of Quality Te...

journal_title：Biometrics

authors： Whittemore AS,Keller JB

更新日期：1986-09-01 00:00:00

abstract：:Let Yi be an ni X 1 vector of observations, Xi an ni X p matrix of known values, and beta an unknown p X 1 with the structure Yi = Xi beta + epsilon i, where the covariance matrix of epsilon i is of intra-class form, that is Cov (epsilon i) = sigma2[(1 - rho) Ii + rho e i e i'] where Ii is the ni X ni identity matrix ...

journal_title：Biometrics

authors： Wiorkowski JJ

更新日期：1975-09-01 00:00:00

abstract：:In studies of serial cancer markers or disease states and their relation to survival, data on the marker or state are usually obtained at infrequent time points during follow-up. A Markov model is developed to assess the dependence of risk of death on marker level or disease state and inferences within this model are ...

journal_title：Biometrics

authors： Kay R

更新日期：1986-12-01 00:00:00

abstract：:We propose a generalized linear mixed model to estimate and test marginal effects on titers repeatedly measured by serial dilution assays. The link is log-log and the titer is assumed to follow a gamma distribution. The parameters are estimated by generalized estimating equations. The marginal effects are tested by me...

journal_title：Biometrics

authors： Bloch J,Chavance M

更新日期：1998-06-01 00:00:00

abstract：:Methods for modeling and mapping spatial variation in disease risk continue to motivate much research. In particular, spatial analyses provide a useful tool for exploring geographical heterogeneity in health outcomes, and consequently can yield clues as to disease etiology, direct public health management, and generat...

journal_title：Biometrics

authors： Costain DA

更新日期：2009-12-01 00:00:00

abstract：:This paper describes methodology for analyzing data from cluster randomized trials with count outcomes, taking indirect effects as well spatial effects into account. Indirect effects are modeled using a novel application of a measure of depth within the intervention arm. Both direct and indirect effects can be estimat...

journal_title：Biometrics

authors： Anaya-Izquierdo K,Alexander N

更新日期：2020-06-18 00:00:00

abstract：:Phase I trials to study the pharmacokinetic properties of a new drug generally involve a restricted number of healthy volunteers. Because of the nature of the group involved in such studies, the appropriate distributional assumptions are not always obvious. These model assumptions include the actual distribution but a...

journal_title：Biometrics

authors： Lindsey JK,Byrom WD,Wang J,Jarvis P,Jones B

更新日期：2000-03-01 00:00:00

abstract：:Cancer population studies based on cancer registry databases are widely conducted to address various research questions. In general, cancer registry databases do not collect information on cause of death. The net survival rate is defined as the survival rate if a subject would not die for any causes other than cancer....

journal_title：Biometrics

authors： Komukai S,Hattori S

更新日期：2017-03-01 00:00:00

abstract：:Highly active antiretroviral therapy (HAART) has proved efficient in increasing CD4 counts in many randomized clinical trials. Because randomized trials have some limitations (e.g., short duration, highly selected subjects), it is interesting to assess the effect of treatments using observational studies. This is chal...

journal_title：Biometrics

authors： Prague M,Commenges D,Gran JM,Ledergerber B,Young J,Furrer H,Thiébaut R

更新日期：2017-03-01 00:00:00

abstract：:Brain evoked potential (EP) data consist of a true response ("signal") and random background activity ("noise"), which are observed over repeated stimulus presentations ("trials"). A signal that changes slowly from trial to trial can be estimated by smoothing across trials and over time within trials. We present a met...

journal_title：Biometrics

authors： Raz J,Turetsky B,Fein G

更新日期：1989-09-01 00:00:00

abstract：:Long-term follow-up is common in many medical investigations where the interest lies in predicting patients' risks for a future adverse outcome using repeatedly measured predictors over time. A key quantity is the likelihood of developing an adverse outcome among individuals who survived up to time s given their covar...

journal_title：Biometrics

authors： Maziarz M,Heagerty P,Cai T,Zheng Y

更新日期：2017-03-01 00:00:00

abstract：:Motivated by the spatial modeling of aberrant crypt foci (ACF) in colon carcinogenesis, we consider binary data with probabilities modeled as the sum of a nonparametric mean plus a latent Gaussian spatial process that accounts for short-range dependencies. The mean is modeled in a general way using regression splines....

journal_title：Biometrics

authors： Apanasovich TV,Ruppert D,Lupton JR,Popovic N,Turner ND,Chapkin RS,Carroll RJ

更新日期：2008-06-01 00:00:00

abstract：:An efficient method is presented for analyses of death rated in one-way or cross-classified experiments where expected survival time for a patient at time of entry on trial is a function of observable covariates. The survival-time distribution used is a Weibull form of Cox's (1972) model. The analysis proceeds in two ...

journal_title：Biometrics

authors： Williams JS

更新日期：1978-06-01 00:00:00

abstract：:To evaluate diagnostic tests, one would ideally like to verify, for example, with a biopsy, the disease state of all subjects in a study. Often, however, no all subjects are verified. Previous methods for evaluation assume that the decision to verify depends only on recorded variables. Sometimes, particularly if the d...

journal_title：Biometrics

authors： Baker SG

更新日期：1995-03-01 00:00:00

abstract：:In multivariate recurrent event data regression, observation of recurrent events is usually terminated by other events that are associated with the recurrent event processes, resulting in informative censoring. Additionally, some covariates could be measured with errors. In some applications, an instrumental variable ...

journal_title：Biometrics

authors： Yu H,Cheng YJ,Wang CY

更新日期：2018-09-01 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：:For many long-lived animal species, individuals do not breed every year, and are often not accessible during non-breeding periods. Individuals exhibit site fidelity if they return to the same breeding colony or spawning ground when they breed. If capture and recapture is only possible at the breeding site, temporary e...

journal_title：Biometrics

authors： Pledger S,Baker E,Scribner K

更新日期：2013-12-01 00:00:00

abstract：:Suppose that a heterogeneous group of individuals is followed over time and that each individual can be in state 0 or state 1 at each time point. The sequence of states is assumed to follow a binary Markov chain. In this paper we model the transition probabilities for the 0 to 0 and 1 to 0 transitions by two logistic ...

journal_title：Biometrics

authors： Muenz LR,Rubinstein LV

更新日期：1985-03-01 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 the problem of testing for a dose-related effect based on a candidate set of (typically nonlinear) dose-response models using likelihood-ratio tests. For the considered models this reduces to assessing whether the slope parameter in these nonlinear regression models is zero or not. A technical problem is t...

journal_title：Biometrics

authors： Gutjahr G,Bornkamp B

更新日期：2017-03-01 00:00:00

abstract：:The basic technical facts of human cytogenetics and the laboratory methods employed in chromosome research are explained in simple terms. The main variables used to describe chromosome images are defined and discussed. Three discriminant analysis models for chromosome classification are developed: one in which each ch...

journal_title：Biometrics

authors： Habbema JD

更新日期：1979-03-01 00:00:00