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作者：Antognini, Alessandro Baldi; Giovagnoli, Alessandra
作者单位：University of Bologna
摘要：In recent years, several authors have investigated response-adaptive allocation rules for comparative clinical trials, in order to favour, at each stage of the trial, the treatment that appears to be best. In this paper, we define admissible allocations, namely treatment assignments that cannot be simultaneously improved upon with respect to both a specific design criterion, reflecting the inferential properties of the experiment, and the proportion of patients assigned to the best treatment o...
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作者：Mueller, Hans-Georg; Yao, Fang
作者单位：University of California System; University of California Davis; University of Toronto
摘要：We consider the problem of estimating functional derivatives and gradients in the framework of a regression setting where one observes functional predictors and scalar responses. Derivatives are then defined as functional directional derivatives that indicate how changes in the predictor function in a specified functional direction are associated with corresponding changes in the scalar response. For a model-free approach, navigating the curse of dimensionality requires the imposition of suita...
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作者：Ferraty, F.; Hall, P.; Vieu, P.
作者单位：Universite de Toulouse; Universite Toulouse III - Paul Sabatier; University of Melbourne
摘要：We suggest a way of reducing the very high dimension of a functional predictor, X, to a low number of dimensions chosen so as to give the best predictive performance. Specifically, if X is observed on a fine grid of design points t(1),..., t(r), we propose a method for choosing a small subset of these, say t(i1),..., t(ik), to optimize the prediction of a response variable, Y. The values t(ij) are referred to as the most predictive design points, or covariates, for a given value of k, and are ...
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作者：Rudas, Tamas; Bergsma, Wicher P.; Nemeth, Renata
作者单位：Eotvos Lorand University; University of London; London School Economics & Political Science
摘要：Models defined by a set of conditional independence restrictions play an important role in statistical theory and applications, especially, but not only, in graphical modelling. In this paper we identify a subclass of these consisting of hierarchical marginal log-linear models, as defined by Bergsma & Rudas (2002a). Such models are smooth, which implies the applicability of standard asymptotic theory and simplifies interpretation. Furthermore, we give a marginal log-linear parameterization and...
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作者：Barr, C. D.; Schoenberg, F. P.
作者单位：Harvard University; University of California System; University of California Los Angeles
摘要：The Voronoi estimator may be defined for any location as the inverse of the area of the corresponding Voronoi cell. We investigate the statistical properties of this estimator for the intensity of an inhomogeneous Poisson process, and demonstrate it is approximately unbiased with a gamma sampling distribution. We also introduce the centroidal Voronoi estimator, a simple extension based on spatial regularization of the point pattern. Simulations show the Voronoi estimator has remarkably low bia...
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作者：Greven, Sonja; Kneib, Thomas
作者单位：University of Munich; Carl von Ossietzky Universitat Oldenburg
摘要：In linear mixed models, model selection frequently includes the selection of random effects. Two versions of the Akaike information criterion, aic, have been used, based either on the marginal or on the conditional distribution. We show that the marginal aic is not an asymptotically unbiased estimator of the Akaike information, and favours smaller models without random effects. For the conditional aic, we show that ignoring estimation uncertainty in the random effects covariance matrix, as is ...
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作者：Wang, Junhui
作者单位：University of Illinois System; University of Illinois Chicago; University of Illinois Chicago Hospital
摘要：In cluster analysis, one of the major challenges is to estimate the number of clusters. Most existing approaches attempt to minimize some distance-based dissimilarity measure within clusters. This article proposes a novel selection criterion that is applicable to all kinds of clustering algorithms, including distance based or non-distance based algorithms. The key idea is to select the number of clusters that minimizes the algorithm's instability, which measures the robustness of any given clu...
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作者：Qian, Jing; Peng, Limin
作者单位：Harvard University; Harvard T.H. Chan School of Public Health; Emory University
摘要：Quantile regression offers a flexible approach to analyzing survival data, allowing each covariate effect to vary with quantiles. In practice, constancy is often found to be adequate for some covariates. In this paper, we study censored quantile regression tailored to the partially functional effect setting with a mixture of varying and constant effects. Such a model can offer a simpler view regarding covariate-survival association and, moreover, can enable improvement in estimation efficiency...
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作者：Chen, Xin; Cook, R. Dennis
作者单位：University of Minnesota System; University of Minnesota Twin Cities
摘要：Continuum regression encompasses ordinary least squares regression, partial least squares regression and principal component regression under the same umbrella using a nonnegative parameter gamma. However, there seems to be no literature discussing the asymptotic properties for arbitrary continuum regression parameter gamma. This article establishes a relation between continuum regression and sufficient dimension reduction and studies the asymptotic properties of continuum regression for arbit...
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作者：Bondell, Howard D.; Reich, Brian J.; Wang, Huixia
作者单位：North Carolina State University
摘要：Since quantile regression curves are estimated individually, the quantile curves can cross, leading to an invalid distribution for the response. A simple constrained version of quantile regression is proposed to avoid the crossing problem for both linear and nonparametric quantile curves. A simulation study and a reanalysis of tropical cyclone intensity data shows the usefulness of the procedure. Asymptotic properties of the estimator are equivalent to the typical approach under standard condi...
