2026-09-23T11:00:08Z https://www.ideals.illinois.edu/oai-pmh

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Shao, Xiaofeng Yang, Yun Shao, Xiaofeng Yang, Yun Chen, Xiaohui Zhu, Ruoqing 2022-05 application/pdf en text Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2024-05-01 The student, Yangfan Zhang, accepted the attached license on 2022-04-18 at 20:11. The student, Yangfan Zhang, submitted this Dissertation for approval on 2022-04-18 at 20:18. This Dissertation was approved for publication on 2022-04-22 at 07:55. DSpace SAF Submission Ingestion Package generated from Vireo submission #17722 on 2022-11-11 at 12:05:54 Statistical inference in high dimensional data and machine learning Zhang, Yangfan 2022-04-22 Statistical Inference High-dimensional Data U-statistics Stochastic Gradient Descent Mean-field Variational Inference This thesis includes four projects. In the first project, we study the non-asymptotic theory of mean-field variational inference and show a BvM theorem for the variational distribution. We propose ELBO as a new criterion for model selection, and demonstrate that it is asymptotically equivalent to BIC but can have better accuracy in terms of evidence approximation. Moreover, we show the geometric convergence of the CAVI algorithm under parametric model framework. In the second project, we propose a class of $L_q$-norm based test statistics, for change point detection in the mean of high-dimensional independent data. We show the asymptotic normality and independence between the statistics with different $q$'s, so that we may combine them to construct an adaptive test with high power against both sparse and dense alternatives. The idea of self-normalization is further applied to avoid variance estimation and leads to pivotal statistics. We also propose a consistent estimator for the change point location, and combine it with a wild binary segmentation algorithm to estimate the change-point number and locations. In the third project, we also propose a class of $L_q$-norm based U-statistics for high-dimensional independent data, but are focused on global testing for model parameters. The statistics are applicable to many testing problems including testing of mean vector and its spatial sign, simultaneous testing of linear model coefficients, and testing of component-wise independence for high-dimensional observations, among others. A variant of the proposed U-statistic with monotone indexes is also considered, with which dynamic programming can be applied to alleviate the computation burden. In the fourth project, we propose an online method based on perturbed SGD to obtain the confidence interval of the true parameters efficiently. The method inherits the online nature of the SGD, and only requires two or four parallel runs of SGD-type algorithms to obtain the confidence interval in any fixed direction. We further combine our method with the UCB algorithm to deal with the bandit problem. Thesis eng https://hdl.handle.net/2142/115556 Copyright 2022 Yangfan Zhang Ph.D. Dissertation Statistics University of Illinois at Urbana-Champaign Statistics