摘要:

SummaryIssues that are central to the understanding and management of the HIV epidemic have generated numerous statistical challenges. This paper considers questions concerning the incubation period, the effects of treatments, pre diction of AIDS cases, the choice of surrogate end points for the assessment of treatments and design of strategies for screening blood samples. These issues give rise to a broad range of intriguing problems for statisticians. We describe some of these problems, how they have been tackled so far and what remains to be done. The discussion touches on topical statistical methods such as smoothing, bootstrapping, interval censoring and the ill‐posed inverse problem, as well as asking fundamental questions for frequentist statistic

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1992.tb01348.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe procedure of Verbyla&Cullis (1990) is extended to cater for the analysis of repeated measures data in which either non‐linear modelling of the treatment contrasts is required and or there are time dependent covariates. These extensions are illustrated via two agricultural data set

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1992.tb01349.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThis paper considers a technique for applying growth curve analysis to data which are correlated across different groups. The method is illustrated using a study comparing three methods of suctioning an endotracheal tube.

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1992.tb01350.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThis paper deals with the regression analysis of failure time data when there are censoring and multiple types of failures. We propose a semiparametric generalization of a parametric mixture model of Larson&Dinse (1985), for which the marginal probabilities of the various failure types are logistic functions of the covariates. Given the type of failure, the conditional distribution of the time to failure follows a proportional hazards model. A marginal like lihood approach to estimating regression parameters is suggested, whereby the baseline hazard functions are eliminated as nuisance parameters. The Monte Carlo method is used to approximate the marginal likelihood; the resulting function is maximized easily using existing software. Some guidelines for choosing the number of Monte Carlo replications are given. Fixing the regression parameters at their estimated values, the full likelihood is maximized via an EM algorithm to estimate the baseline survivor functions. The methods suggested are illustrated using the Stanford heart transplant data.

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1992.tb01351.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThis paper studies a robust approach to the analysis of cell pedigree data, building on the work of Huggins&Marschner (1991) which discussed M‐estimation for the so‐called bifurcating autoregressive process. The study allows for incomplete observation of the pedigree, and incorporates the possibility of additive effects outliers, as discussed in the time series literature. Some properties of the proposed estimation procedure are studied, including a Monte Carlo investigation of robustness in the presence of contaminat

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1992.tb01352.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThis paper is concerned with quasi‐likelihood estimation methods which provide benchmarks in efficiency against which other methods may be as sessed. We discuss general principles and illustrate them by the estimation of parameters for branching processes with immigration and heteroscedastic regression model

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1992.tb01353.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummarySuppose manufactured items have failure times distributed with the two‐parameter exponential density function à‐le‐(x‐μ)/à (x≥μ≥0). The paper considers estimation of the guarantee time μ and mean life after warranty à. Properties of various estimators are given for both separate and simultaneous estimation of μ and à. Criteria for comparing estimators are entropy loss, LINEX loss, and (generaliz

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1992.tb01354.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryRecursive residuals and their relationship to the recursive estimation of regression parameters have been developed for unvaried regression mod els. Such residuals and estimates have been used to test the constancy of regression over time. The current paper extends this work to multivariate regression modal.

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1992.tb01355.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummarySuppose data are collected in a three‐mode fashion (individuals x items X attributes), and it is sought to cluster the individuals into groups on the basis of lineat relations between scores on the attributes for each item and auxiliary measurements made on the same items. A mixture model is pro posed and the EM algorithm is used to fit it to the data by simultaneously estimating the group parameters and allocating individuals to groups. The method is illustrated by a simulation study and a real example in which consumers are clustered on the basis of product scores that are related to a sensory laboratory measuremen

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1992.tb01356.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe ultimate aim of conditioning is to obtain a more relevant estimate of estimation precision by separating experiments of higher precision from those of lower precision. The cost is the information, if any, contained in the conditioning variable. This paper considers the problem of quantifying the costs and benefits of conditioning. Several examples are studied and some of the asymptotic consequences explored.

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1992.tb01357.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY