Better-than-chance classification for signal detection

Jonathan D. Rosenblatt, Yuval Benjamini, Roee Gilron, Roy Mukamel, Jelle J. Goeman

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


The estimated accuracy of a classifier is a random quantity with variability. A common practice in supervised machine learning, is thus to test if the estimated accuracy is significantly better than chance level. This method of signal detection is particularly popular in neuroimaging and genetics. We provide evidence that using a classifier's accuracy as a test statistic can be an underpowered strategy for finding differences between populations, compared to a bona fide statistical test. It is also computationally more demanding than a statistical test. Via simulation, we compare test statistics that are based on classification accuracy, to others based on multivariate test statistics. We find that the probability of detecting differences between two distributions is lower for accuracy-based statistics. We examine several candidate causes for the low power of accuracy-tests. These causes include: the discrete nature of the accuracy-test statistic, the type of signal accuracy-tests are designed to detect, their inefficient use of the data, and their suboptimal regularization. When the purpose of the analysis is the evaluation of a particular classifier, not signal detection, we suggest several improvements to increase power. In particular, to replace V-fold cross-validation with the Leave-One-Out Bootstrap.

Original languageEnglish
Pages (from-to)365-380
Number of pages16
Issue number2
StatePublished - 10 Apr 2021

Bibliographical note

Publisher Copyright:
© The Author 2019. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: [email protected].


  • High dimension
  • Multivariate testing
  • Neuroimaging
  • Statistical genetics
  • Supervised learning


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