摘要:

AbstractData from a litter matched tumorigenesis experiment are analysed using a generalised linear mixed model (GLMM) approach to the analysis of clustered survival data in which there is a dependence of failure time observations within the same litter. Maximum likelihood (ML) and residual maximum likelihood (REML) estimates of risk variable parameters, variance component parameters and the prediction of random effects are given. Estimation of treatment effect parameter (carcinogen effect) has good agreement with previous analyses obtained in the literature though the dependence structure within a litter is modelled in different ways. The variance component estimation provides the estimated dispersion of the random effects. The prediction of random effects, is useful, for instance, in identifying high risk litters and individuals. The present analysis illustrates its wider application to detecting increased risk of occurrence of disease in particular families of a study population.

ISSN:0323-3847    

DOI:10.1002/bimj.4710390102

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractWe investigate the possible bias due to an erroneous missing at random assumption if adjusted odds ratios are estimated from incomplete covariate data using the maximum likelihood principle. A relation between complete case estimates and maximum likelihood estimates allows us to identify situations where the bias vanishes. Numerical computations demonstrate that the bias is most serious if the degree of the violation of the missing at random assumption depends on the value of the outcome variable or of the observed covariate. Implications for the analysis of prospective and retrospective studies are given.

ISSN:0323-3847    

DOI:10.1002/bimj.4710390103

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA new application of LEHMACHER'S (1980) marginal homogeneity sign tests is given by analysis of bivariate response curves (or response surfaces) in two unpaired samples of hypertensive versus normotensive patients. Rationale and computations are illustrated by empirical data from sympathomedullary stress research.

ISSN:0323-3847    

DOI:10.1002/bimj.4710390104

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractAn important issue in epidemiology, often exploratory, is to compare the mortality of a certain cohort, exposed to some dangerous conditions, to that of a reference population. The main statistical tool to study relative mortality has long been the subject‐years method.We propose a Bayesian version of the subject‐years method, particularly suited to analyse the mortality of small cohorts. In particular, we employ the Bayes factor in order to test whether the mortality of a cohort exceeds that of a reference population. The methodology is applied to an occupational epidemiology study. The results are compared to those obtained from the classical one‐sided tests on the same

ISSN:0323-3847    

DOI:10.1002/bimj.4710390105

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractTesting a single change in mean or variance when the observations arenindependent short sequences has not been fully researched in the literature. Two statistical tests, maxtand modified likelihood radtio, are used in this study. Power comparisons and examples are also given. As expected the modified likelihood ratio test yields the largest power. However, with the assumptions we have in the examples, the maxtmight be the optimal method to use. The maxtmay prove useful in assessing departures from the steady state in which the data are short sequences of diagnostic information.

ISSN:0323-3847    

DOI:10.1002/bimj.4710390106

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThis paper reviews a general framework for the modelling of longitudinal data with random measurement times based on marked point processes and presents a worked example. We construct a quite general regression models for longitudinal data, which may in particular include censoring that only depend on the past and outside random variation, and dependencies between measurement times and measurements. The modelling also generalises statistical counting process models. We review a non‐parametric Nadarya‐Watson kernel estimator of the regression function, and a parametric analysis that is based on a conditional least squares (CLS) criterion. The parametric analysis presented, is a conditional version of the generalised estimation equations of LIANG and ZEGER (1986). We conclude that the usual nonparametric and parametric regression modelling can be applied to this general set‐up, with some modifications. The presented framework provides an easily implemented and powerful tool for model building for repeated measure

ISSN:0323-3847    

DOI:10.1002/bimj.4710390107

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe existing measures of diversity within a population and of dissimilarity between two populations postulate a static population with unchanging probabilistic structure. We assume that the measurements associated with an individual change with time according to a stochastic process. General measures of diversity and of dissimilarity when the underlying process is a finite Markov chain are developed. An aportionment of these measures based on a partition of the state‐space is provided. Their asymptotic behaviour is investigated. The spectral analysis of measures of diversity is carried out. Some specific measures of diversity and dissimilarity are obtained when the underlying stochastic process is a general vector‐valued process. An indication of directions for future work is provi

ISSN:0323-3847    

DOI:10.1002/bimj.4710390108

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractNearest Neighbour Balanced Block Designs (NNBD) are widely used in biological and industrial experiments. In this article we examine the optimality and efficiencies of NNBD under various correlated error structure models. A numerical comparison of NNBD with regular block design (RBD) is also presented.

ISSN:0323-3847    

DOI:10.1002/bimj.4710390109

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractPrecedence tests are simple yet robust nonparametric procedures useful for comparing two or more distributions. In this paper precedence‐type tests are considered when the data contain some censored observations. Generalizing the precedence statistic for uncensored data, the precedence tests for censored data are based on the Kaplan‐Meier estimators of the respective distribution functions and the corresponding quantile functions. The literature is reviewed for some two‐sample as well as some multi‐sample p

ISSN:0323-3847    

DOI:10.1002/bimj.4710390110

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe Gompertz distribution has been used to model human mortality and fit actuarial tables. In the recent years, this distribution has been studied by some authors. The MLE estimates for the parameters of the Gompertz distribution were disucssed by GARG, RAO and REDMOND (1970). The purpose of this paper is to develop an exact confidence interval and an exact joint confidence region for the parameters of the Gompertz distribution.

ISSN:0323-3847    

DOI:10.1002/bimj.4710390111

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY