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151.
Malka Gorfine Li Hsu Ross L. Prentice 《Journal of the Royal Statistical Society. Series B, Statistical methodology》2003,65(3):643-661
Summary. In many biomedical studies, covariates are subject to measurement error. Although it is well known that the regression coefficients estimators can be substantially biased if the measurement error is not accommodated, there has been little study of the effect of covariate measurement error on the estimation of the dependence between bivariate failure times. We show that the dependence parameter estimator in the Clayton–Oakes model can be considerably biased if the measurement error in the covariate is not accommodated. In contrast with the typical bias towards the null for marginal regression coefficients, the dependence parameter can be biased in either direction. We introduce a bias reduction technique for the bivariate survival function in copula models while assuming an additive measurement error model and replicated measurement for the covariates, and we study the large and small sample properties of the dependence parameter estimator proposed. 相似文献
152.
CATIA SCRICCIOLO 《Scandinavian Journal of Statistics》2007,34(3):626-642
Abstract. We consider the problem of estimating a compactly supported density taking a Bayesian nonparametric approach. We define a Dirichlet mixture prior that, while selecting piecewise constant densities, has full support on the Hellinger metric space of all commonly dominated probability measures on a known bounded interval. We derive pointwise rates of convergence for the posterior expected density by studying the speed at which the posterior mass accumulates on shrinking Hellinger neighbourhoods of the sampling density. If the data are sampled from a strictly positive, α -Hölderian density, with α ∈ ( 0,1] , then the optimal convergence rate n− α / (2 α +1) is obtained up to a logarithmic factor. Smoothing histograms by polygons, a continuous piecewise linear estimator is obtained that for twice continuously differentiable, strictly positive densities satisfying boundary conditions attains a rate comparable up to a logarithmic factor to the convergence rate n −4/5 for integrated mean squared error of kernel type density estimators. 相似文献
153.
The ability to infer parameters of gene regulatory networks is emerging as a key problem in systems biology. The biochemical
data are intrinsically stochastic and tend to be observed by means of discrete-time sampling systems, which are often limited
in their completeness. In this paper we explore how to make Bayesian inference for the kinetic rate constants of regulatory
networks, using the stochastic kinetic Lotka-Volterra system as a model. This simple model describes behaviour typical of
many biochemical networks which exhibit auto-regulatory behaviour. Various MCMC algorithms are described and their performance
evaluated in several data-poor scenarios. An algorithm based on an approximating process is shown to be particularly efficient. 相似文献
154.
余德才 《河北建筑科技学院学报(社会科学版)》2008,(3):64-67
遵循整体观和相对性理念,在“认知思维模式”基础上,提出了一种无学科界面、自然融合型的科学与人文整合模式,从根本上解决了科学与人文长期以来的分割与对立的局面。并依据该模式提出了“‘组织结构’决定‘性能'”法则、“更大层次系统对系统制约的第一性”的“伦理”法则、“子系统之间和谐共存”法则等思想将引导人类走上“天人合一”的和谐永续的文明道路。 相似文献
155.
The elimination or knockout format is one of the most common designs for pairing competitors in tournaments and leagues. In each round of a knockout tournament, the losers are eliminated while the winners advance to the next round. Typically, the goal of such a design is to identify the overall best player. Using a common probability model for expressing relative player strengths, we develop an adaptive approach to pairing players each round in which the probability that the best player advances to the next round is maximized. We evaluate our method using simulated game outcomes under several data-generating mechanisms, and compare it to random pairings, to the standard knockout format, and to two variants of the standard format. 相似文献
156.
Any continuous bivariate distribution can be expressed in terms of its margins and a unique copula. In the case of extreme‐value distributions, the copula is characterized by a dependence function while each margin depends on three parameters. The authors propose a Bayesian approach for the simultaneous estimation of the dependence function and the parameters defining the margins. They describe a nonparametric model for the dependence function and a reversible jump Markov chain Monte Carlo algorithm for the computation of the Bayesian estimator. They show through simulations that their estimator has a smaller mean integrated squared error than classical nonparametric estimators, especially in small samples. They illustrate their approach on a hydrological data set. 相似文献
157.
Internet环境下的网络教学 总被引:1,自引:0,他引:1
Internet环境下的网络教学已成为人类进行终身教育和创新教育的最佳平台。文章着重论述了Internet环境下的多模式教学———讲授模式、个别辅导模式、讨论学习模式、探索学习模式、协作学习模式 相似文献
158.
We propose four different GMM estimators that allow almost consistent estimation of the structural parameters of panel probit models with fixed effects for the case of small Tand large N. The moments used are derived for each period from a first order approximation of the mean of the dependent variable conditional on explanatory variables and on the fixed effect. The estimators differ w.r.t. the choice of instruments and whether they use trimming to reduce the bias or not. In a Monte Carlo study, we compare these estimators with pooled probit and conditional logit estimators for different data generating processes. The results show that the proposed estimators outperform these competitors in several situations. 相似文献
159.
The authors extend the block external bootstrap to partially linear regression models with strongly mixing, nonstationary error terms. In addition to providing an approximate distribution for the semiparametric least square estimator of the parametric component, they propose a consistent estimator of the co‐variance matrix of this estimator. 相似文献
160.
Tommi Härkänen Hannu Hausen Jorma I. Virtanen Elja Arjas 《Scandinavian Journal of Statistics》2003,30(3):523-533
Abstract A model is introduced here for multivariate failure time data arising from heterogenous populations. In particular, we consider a situation in which the failure times of individual subjects are often temporally clustered, so that many failures occur during a relatively short age interval. The clustering is modelled by assuming that the subjects can be divided into ‘internally homogenous’ latent classes, each such class being then described by a time‐dependent frailty profile function. As an example, we reanalysed the dental caries data presented earlier in Härkänen et al. [Scand. J. Statist. 27 (2000) 577], as it turned out that our earlier model could not adequately describe the observed clustering. 相似文献