What is the primary meaning of "standard deviation"?

Context:  

There was an episode from "Everybody Loves Raymond", which was named "Standard Deviation". In short, Raymond's brother Robert was administering an IQ test for Raymond and his wife Debra. Raymond got 100 points, which according to Robert was average, and Debra scored 115 points. Roberts called that a case of standard deviation and added that that meant that Debra was in a "whole class of higher brains" as compared to Raymond.

Does it mean a deviation from a norm (which is something abnormal) or, rather, a normal deviation (which is a deviation within a normal range)?

While these two meanings seem quite possible to me in this term, they, in fact, are like direct opposites of each other!

Or is it like the actual meaning of this term can only be deduced from context?