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Block-diagonal test for high-dimensional covariance matrices

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Abstract

The structure testing of a high-dimensional covariance matrix plays an important role in financial stock analyses, genetic series analyses, and many other fields. Testing that the covariance matrix is block-diagonal under the high-dimensional setting is the main focus of this paper. Several test procedures that rely on normality assumptions, two-diagonal block assumptions, or sub-block dimensionality assumptions have been proposed to tackle this problem. To relax these assumptions, we develop a test framework based on U-statistics, and the asymptotic distributions of the U-statistics are established under the null and local alternative hypotheses. Moreover, a test approach is developed for alternatives with different sparsity levels. Finally, both a simulation study and real data analysis demonstrate the performance of our proposed methods.

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Acknowledgements

We are grateful to the Editor, the Associate Editor and the two referees for their constructive comments, which helped us to improve the manuscript. The authors thank Prof. Kai Xu for providing the code in Xu and Hao (2019). This paper is supported by the NSFC 12071066 and 12231011.

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Correspondence to Xiaoyi Wang or Shurong Zheng.

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The codes used for the simulations and real data analysis are available upon request from the authors.

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The online supplementary material document contains the proofs of Theorems 1--2 and Proposition 1, proofs of their assisted lemmas, and simulation results of data from the Gamma(4,2)-2 distribution. (pdf 846KB)

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Lai, J., Wang, X., Zhao, K. et al. Block-diagonal test for high-dimensional covariance matrices. TEST 32, 447–466 (2023). https://doi.org/10.1007/s11749-022-00842-x

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  • DOI: https://doi.org/10.1007/s11749-022-00842-x

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