What is math outlier?

Answer 1

There is no standard definition.

If Q1 is the lower quartile and Q3 the upper quartile of a set of observations, then the inter quartile range (IQR) is Q3 - Q1.

Outliers may be defined as values which are smaller than Q1 - k*(IQR) or larger than Q3 + k*IQR where k is some non-negative real number.

Answer 2

An outlier, in statistics, is an observation that is way too large or too small compared with the other observations.

There are various methods of identifying outliers: these can vary according to the nature (skewness) of the underlying distribution of the data.

Answer 3

a number that is distant from most of the other numbers in a list of data