-
作者：Kim, Jae Kwang
作者单位：Iowa State University
摘要：Parametric fractional imputation is proposed as a general tool for missing data analysis. Using fractional weights, the observed likelihood can be approximated by the weighted mean of the imputed data likelihood. Computational efficiency can be achieved using the idea of importance sampling and calibration weighting. The proposed imputation method provides efficient parameter estimates for the model parameters specified in the imputation model and also provides reasonable estimates for paramet...
-
作者：Preston, S. P.; Wood, Andrew T. A.
作者单位：University of Nottingham
摘要：Working within the framework of a multi-dimensional scaling approach to shape analysis, we develop bootstrap methods for inference about mean reflection shape and size-and-shape based on labelled landmark data. The approach is developed in general dimensions though we focus on the three-dimensional case. We consider two pivotal statistics which we use to construct bootstrap confidence regions for the mean reflection shape or size-and-shape, and present simulation results which show that these ...
-
作者：Wang, Jianqiang C.; Opsomer, J. D.
作者单位：Colorado State University System; Colorado State University Fort Collins
摘要：Survey estimators of population quantities such as distribution functions and quantiles contain nondifferentiable functions of estimated quantities. The theoretical properties of such estimators are substantially more complicated to derive than those of differentiable estimators. In this article, we provide a unified framework for obtaining the asymptotic design-based properties of two common types of nondifferentiable estimators. Estimators of the first type have an explicit expression, while...
-
作者：Tang, Cheng Yong; Leng, Chenlei
作者单位：National University of Singapore
摘要：We propose a novel quantile regression approach for longitudinal data analysis which naturally incorporates auxiliary information from the conditional mean model to account for within-subject correlations. The efficiency gain is quantified theoretically and demonstrated empirically via simulation studies and the analysis of a real dataset.
-
作者：Genton, Marc G.; Ma, Yanyuan; Sang, Huiyan
作者单位：Texas A&M University System; Texas A&M University College Station
摘要：We derive a closed form expression for the likelihood function of a Gaussian max-stable process indexed by R-d at p < d+1 sites, d >= 1. We demonstrate the gain in efficiency in the maximum composite likelihood estimators of the covariance matrix from p=2 to p=3 sites in R-2 by means of a Monte Carlo simulation study.
-
作者：Martinussen, Torben; Scheike, Thomas H.; Zucker, David M.
作者单位：University of Copenhagen; University of Copenhagen; Hebrew University of Jerusalem
摘要：In this paper, we consider clustered right-censored time-to-event data. Such data can be analysed either using a marginal model if one is interested in population effects or using so-called frailty models if one is interested in covariate effects on the individual level and in estimation of correlation. The Cox frailty model has been studied extensively in the last decade or so and estimation techniques and large sample results are now available. It is, however, difficult to deal with time-cha...
-
作者：Ramsahai, R. R.; Lauritzen, S. L.
作者单位：University of Cambridge; University of Oxford
摘要：Instrumental variables are widely used for the identification of the causal effect of one random variable on another under unobserved confounding. The distribution of the observable variables for a discrete instrumental variable model satisfies certain inequalities but no conditional independence relations. Such models are usually tested by checking whether the relative frequency estimators of the parameters satisfy the constraints. This ignores sampling uncertainty in the data. Using the obse...
-
作者：Efron, Bradley; Zhang, Nancy R.
作者单位：Stanford University
摘要：Copy number changes, the gains and losses of chromosome segments, are a common type of genetic variation among healthy individuals as well as an important feature in tumour genomes. Microarray technology enables us to simultaneously measure, with moderate accuracy, copy number variation at more than a million chromosome locations and for hundreds of subjects. This leads to massive data sets and complicated inference problems concerning which locations are more likely to vary. In this paper we ...
-
作者：Cardot, Herve; Josserand, Etienne
作者单位：Universite Bourgogne Europe; Centre National de la Recherche Scientifique (CNRS); CNRS - National Institute for Mathematical Sciences (INSMI)
摘要：When dealing with very large datasets of functional data, survey sampling approaches are useful in order to obtain estimators of simple functional quantities, without being obliged to store all the data. We propose a Horvitz-Thompson estimator of the mean trajectory. In the context of a superpopulation framework, we prove, under mild regularity conditions, that we obtain uniformly consistent estimators of the mean function and of its variance function. With additional assumptions on the sampli...
-
作者：Qu, A.; Yi, G. Y.; Song, P. X. -K.; Wang, P.
作者单位：University of Illinois System; University of Illinois Urbana-Champaign; University of Waterloo; University of Michigan System; University of Michigan
摘要：The inverse probability weighted generalized estimating equations approach (Robins et al. 1994; Robins et al. 1995), effectively removes bias and provides valid statistical inference for regression parameter estimation in marginal models when longitudinal data contain missing values. The validity of the weighted generalized estimating equations regarding consistent estimation depends on whether the underlying missing data process is properly modelled. However, there is little work available to...
