# Stats - Outliers

> Source: https://ollybritton.com/notes/a-level/maths/topics/stats/outliers/ · Updated: 2020-11-03 · Tags: maths, stats

##### What is an outlier??
An extreme value.

##### What is an outlier which is not correct called??
An anomaly.

##### What is the process of removing anomalies called??
Cleaning the data.

##### What does $\ll$ mean??
Much less than.

##### What does $\gg$ mean??
Much greater than.

##### What is the typical definition of an outlier??
Any value that is over $1.5$ the interquartile range away from the upper or lower quartile.

##### Should you add an outlier to a box plot??
Yes.

##### Where are the two places a "whisker" should go after you've removed an outlier??
* At the next acceptable value.
* At the outlier boundary.

---
Olly Britton — https://ollybritton.com. Machine-readable index: https://ollybritton.com/llms.txt