2024/03/19 by Bilol Banerjee, Banerjee, Bilol, Anil K. Ghosh +1 · 1 citation
Environmental Science · #Soil Geostatistics and Mapping
paper · pdf · doi:10.48550/arxiv.2403.12491
We develop a test for spherical symmetry of a multivariate distribution Pr that works well even when the dimension of the data d is larger than the sample size n. We propose a non-negative measure of spherical asymmetry ζ(Pr) such that ζ(Pr)=0 if and only if Pr is spherically symmetric. We construct a consistent estimator of ζ(Pr) using the data augmentation method and investigate its large sample properties. The proposed test based on this estimator is calibrated using a novel resampling algorithm. Our test controls the type I error, and it is consistent against general alternatives. We also study its behavior for a sequence of alternatives (1-δn) F+δn G, where ζ(G)=0 but ζ(F)>0, and δn ∈ [0,1]. When limsupδn<1, for any G, the power of our test converges to unity as n increases. However, if limsupδn=1, the asymptotic power of our test depends on lim n(1-δn)2. We establish this by proving the minimax rate optimality of our test over a suitable class of alternatives and showing that it is Pitman efficient when lim n(1-δn)2>0. Moreover, our test is provably consistent for high-dimensional data even when d grows with n. When the center of symmetry is not specified by the null hypothesis, most of the existing tests often fail to satisfy the level property. To take care of this problem, we propose a general recipe for constructing modified tests based on pairwise differences of the observations. Our numerical results amply demonstrate the superiority of the proposed test over some state-of-the-art methods.