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作者：Schwartzman, Armin; Dougherty, Robert F.; Taylor, Jonathan E.
作者单位：Harvard University; Harvard T.H. Chan School of Public Health; Harvard University; Harvard University Medical Affiliates; Dana-Farber Cancer Institute; Stanford University; Stanford University
摘要：Diffusion tensor imaging (DID data differ from most medical images in that values at each voxel are not scalars, but 3 x 3 symmetric positive definite matrices called diffusion tensors (DTs). The anatomic characteristics of the tissue at each voxel are reflected by the DT eigenvalues and eigenvectors. In this article we consider the problem of testing whether the means of two groups of DT images are equal at each voxel in terms of the DT's eigenvalues, eigenvectors, or both. Because eigendecom...
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作者：Zhang, Heping; Liu, Ching-Ti; Wang, Xueqin
作者单位：Yale University; Boston University; Sun Yat Sen University; Sun Yat Sen University
摘要：In many genetics studies, especially in the investigation of mental illness and behavioral disorders, it is common for researchers to collect multiple phenotypes to characterize the complex disease of interest. It may be advantageous to analyze those phenotypic measurements simultaneously if they share a similar genetic mechanism. In this study, we present a nonparametric approach to studying multiple traits together rather than examining each trait separately. Through simulation we compared t...
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作者：Fong, Duncan K. H.; DeSarbo, Wayne S.; Park, Joonwook; Scott, Crystal J.
作者单位：Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; Southern Methodist University; University of Michigan System; University of Michigan
摘要：Multidimensional scaling (MDS) comprises a family of geometric models for the multidimensional representation of data and a corresponding set of methods for fitting such models to actual data. In this paper, we develop a new Bayesian vector MDS model to analyze ordered successive categories preference/dominance data commonly collected in many social science and business studies. A joint spatial representation of the row and column elements of the input data matrix is provided in a reduced dime...
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作者：La Vecchia, Davide; Trojani, Fabio
作者单位：Universita della Svizzera Italiana
摘要：We develop infinitesimally robust statistical procedures for the general diffusion processes. We first prove the existence and uniqueness of the times-series influence function of conditionally unbiased M-estimators for ergodic and stationary diffusions, under weak conditions on the (martingale) estimating function used. We then characterize the robustness of M-estimators for diffusions and derive a class of conditionally unbiased optimal robust estimators. To compute these estimators, we prop...
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作者：Lu, Wenbin; Zhang, Hao Helen
作者单位：North Carolina State University
摘要：We study a general class of partially linear transformation models, which extend linear transformation models by incorporating nonlinear covariate effects in survival data analysis. A new martingale-based estimating equation approach, consisting of both global and kernel-weighted local estimation equations, is developed for estimating the parametric and nonparametric covariate effects in a unified manner. We show that with a proper choice of the kernel bandwidth parameter, one can obtain the c...
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作者：Chan, Yao-ban; Hall, Peter
作者单位：University of Melbourne
摘要：In this paper we develop a nonparametric approach to clustering very high-dimensional data, designed particularly for problems where the mixture nature of a population is expressed through multimodality of its density. Therefore, a technique based implicitly on mode testing can be particularly effective. In principle, several alternative approaches could be used to assess the extent of multimodality, but in the present problem the excess mass method has important advantages. We show that the r...
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作者：Krivobokova, Tatyana; Kneib, Thomas; Claeskens, Gerda
作者单位：University of Gottingen; University of Gottingen; Carl von Ossietzky Universitat Oldenburg; KU Leuven; KU Leuven
摘要：In this article we construct simultaneous confidence bands for a smooth curve using penalized spline estimators. We consider three types of estimation methods: (a) as a standard (fixed effect) nonparametric model, (b) using the mixed-model framework with the spline coefficients as random effects, and (c) a full Bayesian approach. The volume-of-tube formula is applied for the first two methods and compared with Bayesian simultaneous confidence bands from a frequentist perspective. We show that ...
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作者：Spirling, Arthur; Quinn, Kevin
作者单位：Harvard University; University of California System; University of California Berkeley
摘要：Legislative voting records are an important source of information about legislator preferences, intraparty cohesiveness, and the divisiveness of various policy issues. Standard methods of analyzing a legislative voting record tend to have serious drawbacks when applied to legislatures, such as the United Kingdom House of Commons, that feature highly disciplined parties, strategic voting, and large amounts of missing data. We present a method (based on a Dirichlet process mixture model) for ana...
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作者：Rodriguez, Abel; Dunson, David B.; Gelfand, Alan E.
作者单位：University of California System; University of California Santa Cruz; Duke University
摘要：We develop a model for stochastic processes with random marginal distributions. Our model relies on a stick-breaking construction for the marginal distribution of the process, and introduces dependence across locations by using a latent Gaussian copula model as the mechanism for selecting the atoms. The resulting latent stick-breaking process (LaSBP) induces a random partition of the index space, with points closer in space having a higher probability of being in the same cluster. We develop a...
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作者：Cheng, Philip E.; Liou, Michelle; Aston, John A. D.
作者单位：Academia Sinica - Taiwan; University of Warwick
摘要：Likelihood ratio (LR) tests for association and for interaction are examined for three-way contingency tables, particularly the widely used 2 x 2 x K table. Mutual information identities are used to characterize the information decomposition and the logical relationship between the omnibus LR test for conditional independence across K strata and its two independent components. LR tests for interaction and for uniform association. The latter two tests are logically connected to formulating a na...
