How to detect outliers in an ArrayList

java arraylist outliers
Ashton picture Ashton · Sep 14, 2013 · Viewed 15.3k times · Source

I'm trying to think of some code that will allow me to search through my ArrayList and detect any values outside the common range of "good values."

Example: 100 105 102 13 104 22 101

How would I be able to write the code to detect that (in this case) 13 and 22 don't fall within the "good values" of around 100?

Answer

Joni picture Joni · Sep 14, 2013

There are several criteria for detecting outliers. The simplest ones, like Chauvenet's criterion, use the mean and standard deviation calculated from the sample to determine a "normal" range for values. Any value outside of this range is deemed an outlier.

Other criterions are Grubb's test and Dixon's Q test and may give better results than Chauvenet's for example if the sample comes from a skew distribution.

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