摘要:

AbstractThe absolute risk is the probability of developing a given disease over a specified time interval given age and risk factors. GAIL et al. (1989) obtained point estimates for the absolute risk of breast cancer from a population‐based case‐control study, the Breast Cancer Detection and Demonstration Project (BCDDP). They combined relative risk estimates obtained from the case‐control data and based on four risk factors and age, and composite hazard estimates from the cohort data. In this paper, we present a complete analysis of variability for breast cancer absolute risk estimates. Our proposed variance estimator takes into account all components of variability, namely the variances of relative risk estimates and of baseline hazard estimates as well as the covariance between the two, the latter terms being based on implicit delta‐method arguments (BENICHOU and GAIL, 1989). Our variance estimator also takes into account the specifics of the BCDDP study, namely the subsampling of cases and controls. We provide full details of the variance calculations because we anticipate that, in future studies, subsampling will also occur. We also present numerical illustration based on the BCDDP data. These calculations have been used in a recently developed program that computes point estimates and confidence intervals for the absolute risk of breast cancer based on the BCDDP data (BENICHOU

ISSN:0323-3847    

DOI:10.1002/bimj.4710370102

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA deterministic model for the transmission of an acute infectious disease in a heterogeneous, nonrandomly mixing population is developed. This model facilitates the estimation of transmission probabilities from the observed attack rates. If some of the members of the population are vaccinated, then the vaccine efficacy (VE), defined as the relative reduction in the transmission probability due to vaccination, can be estimated. We provide several estimators of VE, depending on the amount of information available on the mixing pattern and on the action of the vaccine. We show that if vaccinated persons increase the frequency of their contacts with infectious persons, then estimators ignoring this change in behavior may substantially underestimate the VE.

ISSN:0323-3847    

DOI:10.1002/bimj.4710370103

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractHidden Markov modelling is a powerful and efficient digital signal processing strategy for extracting the maximum likelihood model from a finite length sample of noisy data. Assuming the number of states in the model is known, then the state levels, transition probabilities, initial state distribution and the noise variance can be estimated. We investigate the applicability of this technique in membrane channel kinetics not only as a parameter estimator, but also as an aid to discriminating between various model types according to their statistical likelihood. We survey three representative classes of channel dynamics, namely: aggregated Markov models, semi‐Markov models (with asymptotically convergent transition probabilities), and coupled Markov models; reformulating each within a discrete‐time hidden Markov model framework. We then provide numerical evidence of the effectiveness of the procedure using simulated channel data and hence show that the correct model, as well as the model parameters, can be discerned. We also demonstrate that the model likelihood can be used to indicate the approximate number of states in the mo

ISSN:0323-3847    

DOI:10.1002/bimj.4710370104

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

ISSN:0323-3847    

DOI:10.1002/bimj.4710370105

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractDesign efficiencies are studied for inferences regarding the coefficients of second‐order models. Subspaces of parameters are identified wherein each of two designs dominates the other locally, or the two designs are equally efficient. Both Fisher efficiency in estimation and Pitman efficiency in hypothesis testing are considered. Eight small second‐order designs ink=3 regressor variables are screened using a four‐part efficiency index. Of these, the central composite, Box‐Behnken, small composite, and hybrid H310 and H311 B designs are found to be generally superior and roughly comparable. Detailed comparisons among these five designs are then undertaken. This work provides further tools for use in design evaluation, requiring only basic matrix operations independently of experiment

ISSN:0323-3847    

DOI:10.1002/bimj.4710370106

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA family of trivariate binomial mixtures with respect to their exponent parameter is introduced and its structure is studied by the use of probability generating functions. Expressions for probabilities, factorial moments and factorial cumulants are given. Conditional distributions are also examined. Illustrative examples include the trivariate Poisson, binomial, negative binomial and modified logarithmic series distributions. In addition, properties of the compounded trivariate Poisson distribution are discussed. Finally biological, medical and ecological applications are indicated.

ISSN:0323-3847    

DOI:10.1002/bimj.4710370107

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

ISSN:0323-3847    

DOI:10.1002/bimj.4710370108

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractWhen a trial involves an invasive laboratory test procedure or requires patients to make a commitment to follow a restrictive test schedule, we can often lose a great proportion of our sampled patients due to refusal of participation into our study. Therefore, incorporating the possible loss of patients into sample size calculation is certainly important in the planning stage of a study. In this paper, we have generalized the sample size calculation procedure for intraclass correlation by accounting for the random loss of patients in the beginning of a trial. We have demonstrated that the simple ad hoc procedure, that raises the estimated sample size in the absence of loss of patients by the factor 1/po, wherepois the retention probability for a randomly selected patient, is adequate whenpois large (=0.80). Whenpois small (i.e., a high refusal rate), however, use of this simple ad hoc procedure tends to underestimate the required sample size. Furthermore, we have found that if the individual retention probability varied substantially among patients, then the magnitude of the above underestimation could even be critical and therefore, the application of the simple direct adjustment procedure in this situation should be avoided.

ISSN:0323-3847    

DOI:10.1002/bimj.4710370109

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

ISSN:0323-3847    

DOI:10.1002/bimj.4710370110

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA bivariate distribution is introduced with marginals convolutions of a binomial and a Poisson random variables. Various properties of the distribution are examined. Estimation is discussed and illustrated by fitting the distribution to two sets of data. An application to ornithology is also indicated.

ISSN:0323-3847    

DOI:10.1002/bimj.4710370111

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY