Generalized estimating equation model for binary outcomes with missing covariates.

abstract：:A formula is derived for determining the number of observations necessary to test the equality of two survival distributions when concomitant information is incorporated. This formula should be useful in designing clinical trials with a heterogeneous patient population. Schoenfeld (1981, Biometrika 68, 316-319) derive...

journal_title：Biometrics

authors： Schoenfeld DA

更新日期：1983-06-01 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：:Serial dilution assays are widely employed for estimating substance concentrations and minimum inhibitory concentrations. The Poisson-Bernoulli model for such assays is appropriate for count data but not for continuous measurements that are encountered in applications involving substance concentrations. This paper pre...

journal_title：Biometrics

authors： Lee ML,Whitmore GA

更新日期：1999-12-01 00:00:00

abstract：:Restricted maximum likelihood (REML) is now well established as a method for estimating the parameters of the general Gaussian linear model with a structured covariance matrix, in particular for mixed linear models. Conventionally, estimates of precision and inference for fixed effects are based on their asymptotic di...

journal_title：Biometrics

authors： Kenward MG,Roger JH

更新日期：1997-09-01 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：:A model specified in terms of linear models for marginal logits and linear models for log-odds ratios is proposed for the analysis of two-period binary cross-over experiments. Hypothesis testing and parameter estimation are facilitated by standard likelihood methodology. Two examples are used to illustrate how the mod...

journal_title：Biometrics

authors： Becker MP,Balagtas CC

更新日期：1993-12-01 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：:A multiple toxicity model for the quantal response of organisms is constructed based on an existing bivariate theory. The main assumption is that the tolerances follow a multivariate normal distribution function. However, any monotone tolerance distribution can be applied by mapping the integration region in the n-dim...

journal_title：Biometrics

authors： Christensen ER,Chen CY

更新日期：1985-09-01 00:00:00

abstract：:Receiver operating characteristic (ROC) analysis is widely used to evaluate the performance of diagnostic tests with continuous or ordinal responses. A popular study design for assessing the accuracy of diagnostic tests involves multiple readers interpreting multiple diagnostic test results, called the multi-reader, m...

journal_title：Biometrics

authors： Kim E,Zhang Z,Wang Y,Zeng D

更新日期：2014-12-01 00:00:00

abstract：:For patients on dialysis, hospitalizations remain a major risk factor for mortality and morbidity. We use data from a large national database, United States Renal Data System, to model time-varying effects of hospitalization risk factors as functions of time since initiation of dialysis. To account for the three-level...

journal_title：Biometrics

authors： Li Y,Nguyen DV,Kürüm E,Rhee CM,Chen Y,Kalantar-Zadeh K,Şentürk D

更新日期：2020-09-01 00:00:00

abstract：:Analysis of longitudinal studies is often complicated through differences amongst individuals in the number and spacing of observations. Laird and Ware (1982, Biometrics 38, 963-974) proposed a linear random-effects model to deal with this problem. We propose a generalisation of this model to accommodate multiple rand...

journal_title：Biometrics

authors： Gilks WR,Wang CC,Yvonnet B,Coursaget P

更新日期：1993-06-01 00:00:00

abstract：:We propose a likelihood-based test for comparing the means of two or more log-normal distributions, with possibly unequal variances. A modification to the likelihood ratio test is needed when sample sizes are small. The performance of the proposed procedures is compared with the F-ratio test using Monte Carlo simulati...

journal_title：Biometrics

authors： Gill PS

更新日期：2004-06-01 00:00:00

abstract：SUMMARY:We develop sample size formulas for studies aiming to test mean differences between a treatment and control group when all-or-none nonadherence (noncompliance) and selection bias are expected. Recent work by Fay, Halloran, and Follmann (2007, Biometrics 63, 465-474) addressed the increased variances within grou...

journal_title：Biometrics

authors： Shardell MD,El-Kamary SS

更新日期：2009-06-01 00:00:00

abstract：:We describe an adaptive Bayesian design for a clinical trial of an experimental treatment for patients with hematologic malignancies who initially received an allogeneic bone marrow transplant but subsequently suffered a disease recurrence. Treatment consists of up to two courses of targeted immunotherapy followed by ...

journal_title：Biometrics

authors： Thall PF,Inoue LY,Martin TG

更新日期：2002-09-01 00:00:00

abstract：:We propose a method to estimate the regression coefficients in a competing risks model where the cause-specific hazard for the cause of interest is related to covariates through a proportional hazards relationship and when cause of failure is missing for some individuals. We use multiple imputation procedures to imput...

journal_title：Biometrics

authors： Lu K,Tsiatis AA

更新日期：2001-12-01 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：:An adjusted rank correlation test is proposed as a technique for identifying publication bias in a meta-analysis, and its operating characteristics are evaluated via simulations. The test statistic is a direct statistical analogue of the popular "funnel-graph." The number of component studies in the meta-analysis, the...

journal_title：Biometrics

authors： Begg CB,Mazumdar M

更新日期：1994-12-01 00:00:00

abstract：:Consider case control analysis with a dichotomous exposure variable that is subject to misclassification. If the classification probabilities are known, then methods are available to adjust odds-ratio estimates in light of the misclassification. We study the realistic scenario where reasonable guesses, but not exact v...

journal_title：Biometrics

authors： Gustafson P,Le ND,Saskin R

更新日期：2001-06-01 00:00:00

abstract：:Stepped wedge designed trials are a type of cluster-randomized study in which the intervention is introduced to each cluster in a random order over time. This design is often used to assess the effect of a new intervention as it is rolled out across a series of clinics or communities. Based on a permutation argument, ...

journal_title：Biometrics

authors： Hughes JP,Heagerty PJ,Xia F,Ren Y

更新日期：2020-03-01 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：:Exposure to high levels of air pollution during the pregnancy is associated with increased probability of preterm birth (PTB), a major cause of infant morbidity and mortality. New statistical methodology is required to specifically determine when a particular pollutant impacts the PTB outcome, to determine the role of...

journal_title：Biometrics

authors： Warren J,Fuentes M,Herring A,Langlois P

更新日期：2012-12-01 00:00:00

abstract：:Drawing inferences for high-dimensional models is challenging as regular asymptotic theories are not applicable. This article proposes a new framework of simultaneous estimation and inferences for high-dimensional linear models. By smoothing over partial regression estimates based on a given variable selection scheme,...

journal_title：Biometrics

authors： Fei Z,Zhu J,Banerjee M,Li Y

更新日期：2019-06-01 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 develop a Bayesian nonparametric mixture modeling framework for quantal bioassay settings. The approach is built upon modeling dose-dependent response distributions. We adopt a structured nonparametric prior mixture model, which induces a monotonicity restriction for the dose-response curve. Particular emphasis is ...

journal_title：Biometrics

authors： Fronczyk K,Kottas A

更新日期：2014-03-01 00:00:00

abstract：:A topic of current biometric discussion is whether stratification should be used in randomized clinical trials and, if so, which kind. An approach based upon randomization theory is used to evaluate pre- versus post-stratification. The results obtained relate specifically to the effect of the size of the clinical tria...

journal_title：Biometrics

authors： McHugh R,Matts J

更新日期：1983-03-01 00:00:00

abstract：:The standard approach to inference for random effects meta-analysis relies on approximating the null distribution of a test statistic by a standard normal distribution. This approximation is asymptotic on k, the number of studies, and can be substantially in error in medical meta-analyses, which often have only a few ...

journal_title：Biometrics

authors： Follmann DA,Proschan MA

更新日期：1999-09-01 00:00:00

abstract：:Five procedures are considered for the comparison of two or more multivariate samples. These procedures include a newly proposed nonparametric rank-sum test and a generalized least squares test. Also considered are the following tests: ordinary least squares, Hotelling's T2, and a Bonferroni per-experiment error-rate ...

journal_title：Biometrics

authors： O'Brien PC

更新日期：1984-12-01 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：:Variable selection for recovering sparsity in nonadditive and nonparametric models with high-dimensional variables has been challenging. This problem becomes even more difficult due to complications in modeling unknown interaction terms among high-dimensional variables. There is currently no variable selection method ...

journal_title：Biometrics

authors： Fang Z,Kim I,Schaumont P

更新日期：2016-12-01 00:00:00

abstract：:A wide variety of similarity indices for comparing two assemblages based on species incidence (i.e., presence/absence) data have been proposed in the literature. These indices are generally based on three simple incidence counts: the number of species shared by two assemblages and the number of species unique to each ...

journal_title：Biometrics

authors： Chao A,Chazdon RL,Colwell RK,Shen TJ

更新日期：2006-06-01 00:00:00