Majumdar, Subhabrata2017-07-182017-07-182017-05https://hdl.handle.net/11299/188932University of Minnesota Ph.D. dissertation. May 2017. Major: Statistics. Advisor: Snigdhansu Chatterjee. 1 computer file (PDF); xiii, 187 pages.Data depth provides a plausible extension of robust univariate quantities like ranks, order statistics and quantiles in multivariate setup. Although depth has gained visibility and has seen many applications in recent years, especially in classification problems for multivariate and functional data, its generalizability and utility in achieving traditional parametric inferential goals is largely unexplored. In this thesis we develop several approaches to address this. In particular, firstly we define an evaluation map function that is more general than data depth, and establish several results in a parametric modelling context using a broad definition of a statistical model. A fast algorithm for covariate selection using data depths as evaluation functions arises as a special case of this. We demonstrate applications of this framework on data from diverse fields: namely climate science, medical imaging and behavioral genetics. Secondly we propose a multivariate rank transformation using data depth and use them for robust inference in location and scale problems in elliptical distributions. Thirdly, we lay out a depth-based regularization framework in multi-response regression, and derive a new method of nonconvex penalized sparse regression in the multitask situation. Across the thesis, several simulation studies and real data examples demonstrate the effectiveness of the methods developed here.enData depthModel selectionMultitask learningPrincipal Component AnalysisrobustnessTwin studiesThesis or Dissertation