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作者：Xu, Jing; Mackenzie, Gilbert
作者单位：University of London; University of Limerick
摘要：It can be more challenging to efficiently model the covariance matrices for multivariate longitudinal data than for the univariate case, due to the correlations arising between multiple responses. The positive-definiteness constraint and the high dimensionality are further obstacles in covariance modelling. In this paper, we develop a data-based method by which the parameters in the covariance matrices are replaced by unconstrained and interpretable parameters with reduced dimensions. The maxi...
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作者：Choi, D. S.; Wolfe, P. J.; Airoldi, E. M.
作者单位：Harvard University; University of London; University College London; Harvard University
摘要：We present asymptotic and finite-sample results on the use of stochastic blockmodels for the analysis of network data. We show that the fraction of misclassified network nodes converges in probability to zero under maximum likelihood fitting when the number of classes is allowed to grow as the root of the network size and the average network degree grows at least poly-logarithmically in this size. We also establish finite-sample confidence bounds on maximum-likelihood blockmodel parameter esti...
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作者：Kim, Yongdai; James, Lancelot; Weissbach, Rafael
作者单位：Seoul National University (SNU); Hong Kong University of Science & Technology; University of Rostock
摘要：Bayesian analysis of a finite state Markov process, which is popularly used to model multistate event history data, is considered. A new prior process, called a beta-Dirichlet process, is introduced for the cumulative intensity functions and is proved to be conjugate. In addition, the beta-Dirichlet prior is applied to a Bayesian semiparametric regression model. To illustrate the application of the proposed model, we analyse a dataset of credit histories.
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作者：Butler, Ronald W.; Bronson, Douglas A.
作者单位：Southern Methodist University; US Department of Veterans Affairs; Veterans Health Administration (VHA)
摘要：Transient semi-Markov processes have traditionally been used to describe the transitions of a patient through the various states of a multistate survival model. A survival distribution in this context is a sojourn through the states until passage to a fatal absorbing state or certain endpoint states. Using complete sojourn data, this paper shows how such survival distributions and associated hazard functions can be estimated nonparametrically and also how nonparametric bootstrap pointwise conf...
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作者：Cox, D. R.; Kartsonaki, Christiana
作者单位：University of Oxford
摘要：Consider parametric models that are too complicated to allow calculation of a likelihood but from which observations can be simulated. We examine parameter estimators that are linear functions of a possibly large set of candidate features. A combination of simulations based on a fractional design and sets of discriminant analyses is then used to find an optimal estimator of the vector parameter and its covariance matrix. The procedure is an alternative to the approximate Bayesian computation s...
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作者：Magirr, D.; Jaki, T.; Whitehead, J.
作者单位：Lancaster University
摘要：We generalize the Dunnett test to derive efficacy and futility boundaries for a flexible multi-arm multi-stage clinical trial for a normally distributed endpoint with known variance. We show that the boundaries control the familywise error rate in the strong sense. The method is applicable for any number of treatment arms, number of stages and number of patients per treatment per stage. It can be used for a wide variety of boundary types or rules derived from alpha-spending functions. Addition...
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作者：Dai, James Y.; Kooperberg, Charles; Leblanc, Michael; Prentice, Ross L.
作者单位：Fred Hutchinson Cancer Center
摘要：Several two-stage multiple testing procedures have been proposed to detect gene-environment interaction in genome-wide association studies. In this article, we elucidate general conditions that are required for validity and power of these procedures, and we propose extensions of two-stage procedures using the case-only estimator of gene-treatment interaction in randomized clinical trials. We develop a unified estimating equation approach to proving asymptotic independence between a filtering s...
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作者：Liu, Aiyi; Liu, Chunling; Zhang, Zhiwei; Albert, Paul S.
作者单位：National Institutes of Health (NIH) - USA; NIH Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD); Hong Kong Polytechnic University
摘要：Several optimality properties of Dorfman's (1943) group testing procedure are derived for estimation of the prevalence of a rare disease whose status is classified with error. Exact ranges of disease prevalence are obtained for which group testing provides more efficient estimation when group size increases.
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作者：Vanderweele, Tyler J.; Tan, Zhiqiang
作者单位：Harvard University; Harvard T.H. Chan School of Public Health; Rutgers University System; Rutgers University New Brunswick
摘要：We give a definition of a bounded edge within the causal directed acyclic graph framework. A bounded edge generalizes the notion of a signed edge and is defined in terms of bounds on a ratio of survivor probabilities. We derive rules concerning the propagation of bounds. Bounds on causal effects in the presence of unmeasured confounding are also derived using bounds related to specific edges on a graph. We illustrate the theory developed by an example concerning estimating the effect of antihi...
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作者：Kim, Yongdai; Kwon, Sunghoon
作者单位：Seoul National University (SNU); University of Minnesota System; University of Minnesota Twin Cities
摘要：Nonconvex penalties such as the smoothly clipped absolute deviation or minimax concave penalties have desirable properties such as the oracle property, even when the dimension of the predictive variables is large. However, checking whether a given local minimizer has such properties is not easy since there can be many local minimizers. In this paper, we give sufficient conditions under which a local minimizer is unique, and show that the oracle estimator becomes the unique local minimizer with...
