# Multiple outliers for two variable linear regression

Problem

Visually, the "extreme" outliers in the following graph are somewhat obvious:

http://i.imgur.com/tiSbS.png

Question

Given:

• T - Set of all temperatures
• Y - Set of all years
• ΣT - Sum of temperatures.
• ΣY - Sum of years.
• N - Number of elements
• T(n) - Temperature of the nth element in the temperature set

How do you determine if T(n) is an outlier?

Related Sites

The math on some of these sites is a bit above my understanding:

Many thanks!

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Although I find the question to be interesting and profound, I removed the set-theory tag, since I don't find it applicable. Perhaps the question could be further retagged? – Joel David Hamkins May 10 '10 at 2:40
If you are looking for practical approaches to outlier removal, you might like to read the answers to mathoverflow.net/questions/6819/…. If you are interested in a philosophical discussion about when it is appropriate to remove outliers (if it ever is) then it appears that Joel might be interested in such a discussion -). – Robby McKilliam May 10 '10 at 3:41