2016

Classification accuracy as a proxy for two sample testing

Kim, Ilmun, Ramdas, Aaditya, Singh, Aarti et al.

Understand

When data analysts train a classifier and check if its accuracy is significantly different from chance, they are implicitly performing a two-sample test.

  • We investigate the statistical properties of this flexible approach in the high-dimensional setting.
  • We prove two results that hold for all classifiers in any dimensions: if its true error remains $\epsilon$-better than chance for some $\epsilon>0$ as $d,n \to \infty$, then (a) the permutation-based test is consistent (has power approaching to one), (b) a computationally efficient test based on a Gaussian approximation of the null distribution is also consistent.
  • To get a finer understanding of the rates of consistency, we study a specialized setting of distinguishing Gaussians with mean-difference $\delta$ and common (known or unknown) covariance $\Sigma$, when $d/n \to c \in (0,\infty)$.

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