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Testing for independence between two random vectors is a fundamental problem in statistics. When the dimension of these two random vectors are fixed, the existing tests based on the distance covariance and Hilbert–Schmidt independence criterion with many desirable properties, including the capacity to capture linear and non-linear dependence. However, these tests may fail to capture the non-linear dependence due to the "curse of dimensionality" when the random vectors are high dimensional. To attack this problem, we propose a general framework for testing the dependence of two random vectors to randomly select two subspaces consisting of components of the vectors, respectively. To enhance the performance of this method, we repeatedly implement this procedure to construct the final test statistic. The new method can also work for non-linear dependence detection in a high-dimensional setup. Theoretically, if the replication time tends to infinity to get the final statistic, we can avoid potential power loss caused by lousy subspaces. Therefore, the two proposed tests are consistent with general alternatives. The weak limit under the null hypothesis is normal; thus, determining critical value need not resort to resampling approximation. We demonstrate the finite-sample performance of the proposed test by using Monte Carlo simulations and the analysis for a real-data example. [ABSTRACT FROM AUTHOR]

We are concerned with massive data which are possibly heterogeneous and scattered at different locations. We introduce a communication-efficient distributed algorithm to estimate the rank-deficient loading matrix in reduced rank regressions. The distributed algorithm, which proceeds iteratively, reduces the computational complexity substantially. During each iteration, it yields a closed-form solution and refines the previous estimators gradually. After a finite number of iterations, the final solution estimates the rank consistently, and more importantly, achieves the oracle rate. We recast sufficient dimension reduction methods under the framework of reduced rank regressions, which enables us to recover the central subspace and simultaneously estimate its structural dimension. We demonstrate the efficiency of our proposed distributed algorithm through simulations and an application to the airline on-line performance dataset consisting of 118,914,458 observations. [ABSTRACT FROM AUTHOR]

In this paper, from the estimating equation-based sufficient dimension reduction method in the literature, its robust version is proposed to alleviate the impact from outliers. To achieve this, a robust nonparametric regression estimator is suggested. The estimator is plugged in the estimating equation of the semiparametric sufficient dimension reduction to obtain robust estimator for the central subspace. The asymptotic properties and robustness of the estimator are investigated. Numerical simulation and real data analysis are conducted to examine the performance of the estimators. [ABSTRACT FROM AUTHOR]

Abstract: This paper considers estimation of the semiparametric multi-index model with missing covariates at random. A weighted estimating equation is suggested by invoking the inverse selection probability approach, and estimators of the indices are respectively defined when the selection probability is known in advance, is estimated parametrically and nonparametrically. The consistency is provided. For the single-index model, the large sample properties show that the estimators with both parametric and nonparametric plug-in estimations can play an important role to achieve smaller limiting variances than the estimator with the true selection probability. Simulation studies are carried out to assess the finite sample performance of the proposed estimators. The proposed methods are applied to an AIDS clinical trials dataset to examine which method could be more efficient. A horse colic dataset is also analyzed for illustration. [Copyright &y& Elsevier]

Abstract: In this paper, we consider subset deletion diagnostics for fixed effects (coefficient functions), random effects and one variance component in varying coefficient mixed models (VCMMs). Some simple updated formulas are obtained, and based on which, Cook’s distance, joint influence and conditional influence are also investigated. Besides, since mean shift outlier models (MSOMs) are also efficient to detect outliers, we establish an equivalence between deletion models and MSOMs, which is not only suitable for fixed effects but also for random effects, and test statistics for outliers are then constructed. As a byproduct, we obtain the nonparametric “delete = replace” identity. Our influence diagnostics methods are illustrated through a simulated example and a real data set. [Copyright &y& Elsevier]

The Wilcoxon–Mann–Whitney test is designed to test homogeneity of two random samples in the univariate case. It is very powerful to detect location shifts yet may lose power completely when there exist scale differences. We generalize the classic Wilcoxon–Mann–Whitney test through using pairwise distances of all observations. The generalized test can be readily used even when the random observations are multivariate. It is also very powerful in the presence of scale differences. The generalized test is in spirit to compare difference between the distribution functions of two random samples. It is m n / (m + n) -consistent under the strong null and local alternatives, and root- m n / (m + n) -consistent under fixed alternatives, where m , n stand for the respective sizes of the two random samples. The power of the generalized test is asymptotically independent of m / n , the size ratio of the two random samples. This indicates that the generalized test has nontrivial power as long as the sample sizes are not extremely unbalanced. We demonstrate the theoretical properties of our improved rank-based two-sample test through comprehensive numerical studies. [ABSTRACT FROM AUTHOR]

Testing for homogeneity of two random vectors is a fundamental problem in statistics. In the past two decades, numerous efforts have been made to detect heterogeneity when the random vectors are multivariate or even high dimensional. Due to the "curse of dimensionality", existing tests based on Euclidean distance may fail to capture the overall homogeneity in high-dimensional settings while can only capture the moment discrepancy. To address this issue, we propose a fully nonparametric test for homogeneity of two random vectors. Our method involves randomly selecting two subspaces consisting of components of the vectors, projecting the subspaces onto one-dimensional spaces, respectively, and constructing the test statistic using the Cramér–von Mises distance of the projections. To enhance the performance, we repeatedly implement this procedure to construct the final test statistic. Theoretically, if the replication time tends to infinity, we can avoid potential power loss caused by lousy directions. Owing to the U -statistic theory, the asymptotic null distribution of our proposed test is standard normal, regardless of the parent distributions of the random samples and the relationship between data dimensions and sample sizes. As a result, no re-sampling procedure is needed to determine critical values. The empirical size and power of the proposed test are demonstrated through numerical simulations. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we propose a nonparametric independence screening method for sparse ultra-high dimensional generalized varying coefficient models with longitudinal data. Our methods combine the ideas of sure independence screening (SIS) in sparse ultra-high dimensional generalized linear models and varying coefficient models with the marginal generalized estimating equation (GEE) method, called NIS-GEE, considering both the marginal correlation between response and covariates, and the subject correlation for variable screening. The corresponding iterative algorithm is introduced to enhance the performance of the proposed NIS-GEE method. Furthermore it is shown that, under some regularity conditions, the proposed NIS-GEE method enjoys the sure screening properties. Simulation studies and a real data analysis are used to assess the performance of the proposed method. [ABSTRACT FROM AUTHOR]