摘要:

AbstractAfter a short review of the development of the modern approach to the design of clinical trials, attention is focused on the wide variety of trials, their ethical constraints, the criteria for stopping trials, and the possible use of Bayesian methods. Brief discussions are then presented of two specific topics: the analysis of categorical data, and the replication of trials with the consequent need for overviews.

ISSN:0319-5724    

DOI:10.2307/3315570

出版商:Wiley‐Blackwell    

年代:1992

数据来源: WILEY

摘要:

AbstractSuppose that ϕ is a Gaussian density and that g = f * ϕ, where * denotes convolution. From observations with density g, one wishes to estimate f. We analyze an estimate which is a linear combination of estimates of derivatives of g and show that this estimate converges in an L2norm at a rate which is compatible with the pointwise optimal rate established by Fan (1991

ISSN:0319-5724    

DOI:10.2307/3315571

出版商:Wiley‐Blackwell    

年代:1992

数据来源: WILEY

摘要:

AbstractIt has been recognized that counting the objects allocated by a rule of classification to several unknown classes often does not provide good estimates of the true class proportions of the objects to be classified. We propose a linear transformation of these classification estimates, which minimizes the mean squared error of the transformed estimates over all possible sets of true proportions. This so‐called best‐linear‐corrector (BLC) transformation is a function of the confusion (classification‐error) matrix and of the first and second moments of the prior distribution of the vector of proportions. When the number of objects to be classified increases, the BLC tends to the inverse of the confusion matrix. The estimates that are obtained directly by this inverse‐confusion corrector (ICC) are also the maximum‐likelihood unbiased estimates of the probabilities that the objects originate from one or the other class, had the objects been preselected with those probabilities. But for estimating the actual proportions, the ICC estimates behave less well than the raw classification estimates for some collections. In that situation, the BLC is substantially superior to the ICC even for some large collections of objects and is always substantially superior to the raw estimates. The statistical model is applied concretely to the measure of forest covers in rem

ISSN:0319-5724    

DOI:10.2307/3315572

出版商:Wiley‐Blackwell    

年代:1992

数据来源: WILEY

摘要:

AbstractEstimation of a smooth function is considered when observations on this function added with Gaussian errors are observed. The problem is formulated as a general linear model, and a hierarchical Bayesian approach is then used to study it. Credible bands are also developed for the function. Sensitivity analysis is conducted to determine the influence of the choice of priors on hyperparameters. Finally, the methodology is illustrated using real and simulated examples where it is compared with classical cubic splines. It is also shown that our approach provides a Bayesian solution to some problems in discrete time series.

ISSN:0319-5724    

DOI:10.2307/3315573

出版商:Wiley‐Blackwell    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper studies the application of the orthogonalization technique of Cox and Reid (1987) to parametric families of link functions used in binary regression analysis. The explicit form of Cox and Reid's condition (4), for orthogonality at a point, is derived for arbitrary link families. This condition is used to determine a transform of a family introduced by Burr (1942) and Prentice (1975, 1976) which is locally orthogonal when the regression parameter is zero. Thus the benefits of having orthogonal parameters are limited to “small” regression effects. The extent to which approximate orthogonality holds for nonzero regression coefficients is investigated for two data sets from the literature. Two specific issues considered are: (1) the ability of orthogonal reparametrization to reduce the variability of the regression parameters caused by estimation of the link parameter and (2) the improved numerical stability (and hence interpretability) of regression estimates corresponding to different link paramet

ISSN:0319-5724    

DOI:10.2307/3315574

出版商:Wiley‐Blackwell    

年代:1992

数据来源: WILEY

摘要:

AbstractInference for a scalar interest parameter in the presence of nuisance parameters is considered in terms of the conditional maximum‐likelihood estimator developed by Cox and Reid (1987). Parameter orthogonality is assumed throughout. The estimator is analyzed by means of stochastic asymptotic expansions in three cases: a scalar nuisance parameter, m nuisance parameters from m independent samples, and a vector nuisance parameter. In each case, the expansion for the conditional maximum‐likelihood estimator is compared with that for the usual maximum‐likelihood estimator. The means and variances are also compared. In each of the cases, the bias of the conditional maximum‐likelihood estimator is unaffected by the nuisance parameter to first order. This is not so for the maximum‐likelihood estimator. The assumption of parameter orthogonality is crucial in attaining this result. Regardless of parametrization, the difference in the two estimators is first‐order and is deterministic to

ISSN:0319-5724    

DOI:10.2307/3315575

出版商:Wiley‐Blackwell    

年代:1992

数据来源: WILEY

摘要:

AbstractNecessary and sufficient conditions for weak and strong convergence are derived for the weighted version of a general process under random censoring. To be more explicit, this means that for this process complete analogues are obtained of the Chibisov‐O'Reilly theorem, the Lai‐Wellner Glivenko‐Cantelli theorem, and the James law of the iterated logarithm for the empirical process. The process contains as special cases the so‐called basic martingale, the empirical cumulative hazard process, and the product‐limit process. As a tool we derive a Kiefer‐process‐type approximation of our process, which may be of indepen

ISSN:0319-5724    

DOI:10.2307/3315576

出版商:Wiley‐Blackwell    

年代:1992

数据来源: WILEY

ISSN:0319-5724    

DOI:10.2307/3315578

出版商:Wiley‐Blackwell    

年代:1992

数据来源: WILEY

ISSN:0319-5724    

DOI:10.2307/3315579

出版商:Wiley‐Blackwell    

年代:1992

数据来源: WILEY

ISSN:0319-5724    

DOI:10.2307/3315580

出版商:Wiley‐Blackwell    

年代:1992

数据来源: WILEY