I signed up for a Math Mentorship Program (for high school students) this term, but one of the students assigned to me is more interested in Statistics and Finance - something that would help him to do business :-)

The closest I could come up with (using ideas of a friend) is some game theoretic stuff like price of anarchy (a related and possibly with much simpler mathematics is The Economics of Caste and of the Rat Race and Other Woeful Tales by Akerlof), Arrow's Impossibility Theorem, and possibly some Prospect theory.

Does anyone have any idea about elementary interesting math related to Statistics or Finance?