What are some techniques that I can use for anomaly detection given a non-Normal distribution? I have less than twenty available observations.

  • $\begingroup$ Checkout QQ plots also with what JahKnows said.. $\endgroup$
    – Aditya
    Mar 22, 2018 at 13:07
  • $\begingroup$ @JahKnows - if the offer still stands, I would like to ask for an easy introduction. $\endgroup$ Mar 11, 2019 at 11:43
  • $\begingroup$ @user7677771, probably best to ask a separate question to avoid reviving old posts. But, sure! $\endgroup$
    – JahKnows
    Mar 12, 2019 at 0:41

1 Answer 1


I would suggest a nearest neighbors approach. This technique is non-parametric, such that it does not assume your features follow any given distribution. The degree from which a novel instance can be classified as anomalous can set through some p-value estimation. These techniques are computationally expensive however due to your small dataset this may be well suited.

Check out:

Learning Minimum Volume Sets http://www.stat.rice.edu/~cscott/pubs/minvol06jmlr.pdf

Anomaly Detection with Score functions based on Nearest Neighbor Graphs https://arxiv.org/abs/0910.5461

New statistic in P-value estimation for anomaly detection http://ieeexplore.ieee.org/document/6319713/

You can also use more rudimentary anomaly detection techniques such as a generalized likelihood ratio test. But, this is kind of old-school.

  • $\begingroup$ I can elaborate on how these techniques work if you have difficulty with the paper. They're relatively easy concepts clouded in a lot of theory in the papers. $\endgroup$
    – JahKnows
    Mar 22, 2018 at 10:52
  • $\begingroup$ Does this approach work with non-negative distributions as well? $\endgroup$
    – Maxim
    Jun 23, 2022 at 16:29

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