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 Author:
 Leung, Denis HengâYan; Wang, YouâGan
 Source:
 Biometrics 2001 v.57 no.1 pp. 309312
 ISSN:
 0006341X
 Subject:
 Bayesian theory; biometry; probability
 Abstract:
 ... Stallard (1998, Biometrics54, 279â294) recently used Bayesian decision theory for sampleâsize determination in phase II trials. His design maximizes the expected financial gains in the development of a new treatment. However, it results in a very high probability (0.65) of recommending an ineffective treatment for phase III testing. On the other hand, the expected gain using his design is more ...
 DOI:
 10.1111/j.0006341X.2001.00309.x

http://dx.doi.org/10.1111/j.0006341X.2001.00309.x
 Author:
 Mancl, Lloyd A.; DeRouen, Timothy A.
 Source:
 Biometrics 2001 v.57 no.1 pp. 126134
 ISSN:
 0006341X
 Subject:
 biometry; bone resorption; covariance; equations; periodontal diseases; randomized clinical trials
 Abstract:
 ... In this paper, we propose an alternative covariance estimator to the robust covariance estimator of generalized estimating equations (GEE). Hypothesis tests using the robust covariance estimator can have inflated size when the number of independent clusters is small. Resampling methods, such as the jackknife and bootstrap, have been suggested for covariance estimation when the number of clusters i ...
 DOI:
 10.1111/j.0006341X.2001.00126.x

http://dx.doi.org/10.1111/j.0006341X.2001.00126.x
 Author:
 Naranjo, Joshua D.; McKean, Joseph W.
 Source:
 Biometrics 2001 v.57 no.1 pp. 178181
 ISSN:
 0006341X
 Subject:
 biometry; clinical trials; models; patients; therapeutics
 Abstract:
 ... When clinical studies require enrolled patients to have abnormal assays, the natural tendency of repeat measurements to regress toward the mean can lead to a false assessment of effectiveness of therapy. We propose a method to more accurately estimate the true effect of therapy by adjusting for a component of improvement that can be attributed to regression effect. The model we use allows for a co ...
 DOI:
 10.1111/j.0006341X.2001.00178.x

http://dx.doi.org/10.1111/j.0006341X.2001.00178.x
 Author:
 Pan, Wei
 Source:
 Biometrics 2001 v.57 no.1 pp. 120125
 ISSN:
 0006341X
 Subject:
 biometry; data collection; equations; regression analysis
 Abstract:
 ... Correlated response data are common in biomedical studies. Regression analysis based on the generalized estimating equations (GEE) is an increasingly important method for such data. However, there seem to be few model‐selection criteria available in GEE. The well‐known Akaike Information Criterion (AIC) cannot be directly applied since AIC is based on maximum likelihood estimation while GEE is non ...
 DOI:
 10.1111/j.0006341X.2001.00120.x

http://dx.doi.org/10.1111/j.0006341X.2001.00120.x
 Author:
 Chatterjee, Nilanjan; Wacholder, Sholom
 Source:
 Biometrics 2001 v.57 no.1 pp. 245252
 ISSN:
 0006341X
 Subject:
 biometry; genotype; mutation; penetrance
 Abstract:
 ... The kinâcohort design is a promising alternative to traditional cohort or caseâcontrol designs for estimating penetrance of an identified rare autosomal mutation. In this design, a suitably selected sample of participants provides genotype and detailed family history information on the disease of interest. To estimate penetrance of the mutation, we consider a marginal likelihood approach that ...
 DOI:
 10.1111/j.0006341X.2001.00245.x

http://dx.doi.org/10.1111/j.0006341X.2001.00245.x
 Author:
 Inglis, Iain M.; Gray, Alison J.
 Source:
 Biometrics 2001 v.57 no.1 pp. 232239
 ISSN:
 0006341X
 Subject:
 algorithms; biometry; fungi; hyphae; image analysis
 Abstract:
 ... Semiautomatic image analysis techniques are particularly useful in biological applications, which commonly generate very complex images, and offer considerable flexibility. However, systematic study of such methods is lacking; most research develops fully automatic algorithms. This paper describes a study to evaluate several different semiautomatic or computer‐assisted approaches to contour segmen ...
 DOI:
 10.1111/j.0006341X.2001.00232.x

http://dx.doi.org/10.1111/j.0006341X.2001.00232.x
 Author:
 Ridout, Martin; Hinde, John; DemÃ©Atrio, Clarice G. B.
 Source:
 Biometrics 2001 v.57 no.1 pp. 219223
 ISSN:
 0006341X
 Subject:
 biometry; models; regression analysis
 Abstract:
 ... Count data often show a higher incidence of zero counts than would be expected if the data were Poisson distributed. Zeroâinflated Poisson regression models are a useful class of models for such data, but parameter estimates may be seriously biased if the nonzero counts are overdispersed in relation to the Poisson distribution. We therefore provide a score test for testing zeroâinflated Poisso ...
 DOI:
 10.1111/j.0006341X.2001.00219.x

http://dx.doi.org/10.1111/j.0006341X.2001.00219.x
 Author:
 Heinze, Georg; Schemper, Michael
 Source:
 Biometrics 2001 v.57 no.1 pp. 114119
 ISSN:
 0006341X
 Subject:
 biometry; breast neoplasms; confidence interval; models; regression analysis
 Abstract:
 ... The phenomenon of monotone likelihood is observed in the fitting process of a Cox model if the likelihood converges to a finite value while at least one parameter estimate diverges to Â±â. Monotone likelihood primarily occurs in small samples with substantial censoring of survival times and several highly predictive covariates. Previous options to deal with monotone likelihood have been unsatisf ...
 DOI:
 10.1111/j.0006341X.2001.00114.x

http://dx.doi.org/10.1111/j.0006341X.2001.00114.x
 Author:
 Dendukuri, Nandini; Joseph, Lawrence
 Source:
 Biometrics 2001 v.57 no.1 pp. 158167
 ISSN:
 0006341X
 Subject:
 Bayesian theory; Strongyloides; diagnostic techniques; disease prevalence; models; refugees; strongylosis; uncertainty; Cambodia; Canada
 Abstract:
 ... Many analyses of results from multiple diagnostic tests assume the tests are statistically independent conditional on the true disease status of the subject. This assumption may be violated in practice, especially in situations where none of the tests is a perfectly accurate gold standard. Classical inference for models accounting for the conditional dependence between tests requires that results ...
 DOI:
 10.1111/j.0006341X.2001.00158.x

http://dx.doi.org/10.1111/j.0006341X.2001.00158.x
 Author:
 Carey, Vincent J.; Baker, Carol J.; Platt, Richard
 Source:
 Biometrics 2001 v.57 no.1 pp. 135142
 ISSN:
 0006341X
 Subject:
 Bayesian theory; biometry; immune response; pathogens; patients; risk
 Abstract:
 ... In the study of immune responses to infectious pathogens, the minimum protective antibody concentration (MPAC) is a quantity of great interest. We use caseâcontrol data to estimate the posterior distribution of the conditional risk of disease given a lower bound on antibody concentration in an atârisk subject. The concentration bound beyond which there is high credibility that infection risk i ...
 DOI:
 10.1111/j.0006341X.2001.00135.x

http://dx.doi.org/10.1111/j.0006341X.2001.00135.x
 Author:
 Denison, D. G. T.; Holmes, C. C.
 Source:
 Biometrics 2001 v.57 no.1 pp. 143149
 ISSN:
 0006341X
 Subject:
 biometry; leukemia; models; risk; New York
 Abstract:
 ... This paper presents a Bayesian nonlinear approach for the analysis of spatial count data. It extends the Bayesian partition methodology of Holmes, Denison, and Mallick (1999, Bayesian partitioning for classification and regression, Technical Report, Imperial College, London) to handle data that involve counts. A demonstration involving incidence rates of leukemia in New York state is used to highl ...
 DOI:
 10.1111/j.0006341X.2001.00143.x

http://dx.doi.org/10.1111/j.0006341X.2001.00143.x
 Author:
 Dominici, Francesca; Parmigiani, Giovanni
 Source:
 Biometrics 2001 v.57 no.1 pp. 150157
 ISSN:
 0006341X
 Subject:
 biometry; congenital abnormalities; developmental toxicity; diagnostic techniques; dose response; logit analysis; models; probability; toxicity testing
 Abstract:
 ... Modeling of developmental toxicity studies often requires simple parametric analyses of the dose‐response relationship between exposure and probability of a birth defect but poses challenges because of nonstandard distributions of birth defects for a fixed level of exposure. This article is motivated by two such experiments in which the distribution of the outcome variable is challenging to both t ...
 DOI:
 10.1111/j.0006341X.2001.00150.x

http://dx.doi.org/10.1111/j.0006341X.2001.00150.x
 Author:
 Fitzmaurice, Garrett M.; Lipsitz, Stuart R.; Molenberghs, Geert; Ibrahim, Joseph G.
 Source:
 Biometrics 2001 v.57 no.1 pp. 1521
 ISSN:
 0006341X
 Subject:
 biometry; covariance; equations
 Abstract:
 ... This paper considers the impact of bias in the estimation of the association parameters for longitudinal binary responses when there are dropâouts. A number of different estimating equation approaches are considered for the case where dropâout cannot be assumed to be a completely random process. In particular, standard generalized estimating equations (GEE), GEE based on conditional residuals, ...
 DOI:
 10.1111/j.0006341X.2001.00015.x

http://dx.doi.org/10.1111/j.0006341X.2001.00015.x
 Author:
 Dauk, Philip C.; Schwarz, Carl J.
 Source:
 Biometrics 2001 v.57 no.1 pp. 287293
 ISSN:
 0006341X
 Subject:
 fisheries; fishermen; freshwater fish; gillnets; models; rivers; surveys; variance; British Columbia
 Abstract:
 ... One strategy for estimating total catch is to employ two separate surveys that independently estimate total fishing effort and catch rate with the estimator for total catch formed by their product. Survey designs for estimating catch rate often involve interviewing the fishermen during their fishing episodes. Such roving designs result in incomplete episode data and characteristically have employe ...
 DOI:
 10.1111/j.0006341X.2001.00287.x

http://dx.doi.org/10.1111/j.0006341X.2001.00287.x
 Author:
 Lindberg, M. S.; Kendall, W. L.; Hines, J. E.; Anderson, Michael G.
 Source:
 Biometrics 2001 v.57 no.1 pp. 273281
 ISSN:
 0006341X
 Subject:
 Markov chain; adults; biometry; ducks; models
 Abstract:
 ... Captureârecapture models are widely used to estimate demographic parameters of marked populations. Recently, this statistical theory has been extended to modeling dispersal of open populations. Multistate models can be used to estimate movement probabilities among subdivided populations if multiple sites are sampled. Frequently, however, sampling is limited to a single site, Models described by ...
 DOI:
 10.1111/j.0006341X.2001.00273.x

http://dx.doi.org/10.1111/j.0006341X.2001.00273.x
 Author:
 Straws, Warren J.; Carroll, Raymond J.; Bortnick, Steven M.; Menkedick, John R.; Schultz, Bradley D.
 Source:
 Biometrics 2001 v.57 no.1 pp. 203210
 ISSN:
 0006341X
 Subject:
 air pollution; blood; children; data collection; exposure assessment; lead; models; paints; prediction; residential housing
 Abstract:
 ... A model for children's blood lead concentrations as a function of environmental lead exposures was developed by combining two nationally representative sources of data that characterize the marginal distributions of blood lead and environmental lead with a third regional dataset that contains joint measures of blood lead and environmental lead. The complicating factor addressed in this article was ...
 DOI:
 10.1111/j.0006341X.2001.00203.x

http://dx.doi.org/10.1111/j.0006341X.2001.00203.x
 Author:
 McShane, Lisa M.; Midthune, Douglas N.; Dorgan, Joanne F.; Freedman, Laurence S.; Carroll, Raymond J.
 Source:
 Biometrics 2001 v.57 no.1 pp. 6273
 ISSN:
 0006341X
 Subject:
 biometry; blood serum; casecontrol studies; equations; odds ratio; prostatic neoplasms
 Abstract:
 ... We propose a conditional scores procedure for obtaining biasâcorrected estimates of log odds ratios from matched caseâcontrol data in which one or more covariates are subject to measurement error. The approach involves conditioning on sufficient statistics for the unobservable true covariates that are treated as fixed unknown parameters. For the case of Gaussian nondifferential measurement err ...
 DOI:
 10.1111/j.0006341X.2001.00062.x

http://dx.doi.org/10.1111/j.0006341X.2001.00062.x
 Author:
 Dean, C. B.; Ugarte, M. D.; Militino, A. F.
 Source:
 Biometrics 2001 v.57 no.1 pp. 197202
 ISSN:
 0006341X
 Subject:
 age; epidemiology; human diseases; models; mortality; relative risk; British Columbia
 Abstract:
 ... The purpose of this article is to draw attention to the possible need for inclusion of interaction effects between regions and age groups in mapping studies. We propose a simple model for including such an interaction in order to develop a test for its significance. The assumption of an absence of such interaction effects is a helpful simplifying one. The measure of relative risk related to a part ...
 DOI:
 10.1111/j.0006341X.2001.00197.x

http://dx.doi.org/10.1111/j.0006341X.2001.00197.x
 Author:
 Greenland, Sander
 Source:
 Biometrics 2001 v.57 no.1 pp. 182188
 ISSN:
 0006341X
 Subject:
 biometry; casecontrol studies; childhood; leukemia; public health; regression analysis; surveys; United States
 Abstract:
 ... Standard presentations of epidemiological results focus on incidenceâratio estimates derived from regression models fit to specialized study data. These data are often highly nonrepresentative of populations for which publicâhealth impacts must be evaluated. Basic methods are provided for interval estimation of attributable fractions from modelâbased incidenceâratio estimates combined with ...
 DOI:
 10.1111/j.0006341X.2001.00182.x

http://dx.doi.org/10.1111/j.0006341X.2001.00182.x
 Author:
 Dunson, David B.; Perreault, Sally D.
 Source:
 Biometrics 2001 v.57 no.1 pp. 302308
 ISSN:
 0006341X
 Subject:
 Markov chain; Monte Carlo method; data analysis; linear models; reproductive toxicology; spermatozoa; toxicity
 Abstract:
 ... This article describes a general class of factor analytic models for the analysis of clustered multivariate data in the presence of informative missingness. We assume that there are distinct sets of cluster‐level latent variables related to the primary outcomes and to the censoring process, and we account for dependency between these latent variables through a hierarchical model. A linear model is ...
 DOI:
 10.1111/j.0006341X.2001.00302.x

http://dx.doi.org/10.1111/j.0006341X.2001.00302.x