What Is the Interquartile Range Rule?

https://www.thoughtco.com/what-is-the-interquartile-range-rule-3126244

How Are Outliers Determined in Statistics?

https://www.thoughtco.com/what-is-an-outlier-3126227

@Karabiner I was kind of thinking of the opposite scenario. Where faulty or different DGP derived observation, removed then makes two groups more comparable or not a different. But as eluded to, there are many definitions and rationales for sleuthing them out.