Friday, 2 December 2011

Simpson's Paradox

The answer to the recent poll question "Player A has a higher batting average than Player B in three consecutive years. When the three years are combined, will Player A always have the highest average?" is, counter-intuitively, No.

This is little known to non-statisticians, but it is quite possible for an average to be higher in a number of individual events, yet when the numbers are combined, for the 'poorer' record to come out on top.

Wikipedia uses a few real-life examples, one sports related, using batting averages in baseball for two well-known DJs. In all three years from 1995 to 1997, David Justice had a higher batting average than Derek Jeter:

Who had the higher batting average overall? Of course, it’s not David Justice, who averages out over the three years at .298 (213/1046), but Derek Jeter whose combined totals of 385/1284 give him an average of .300.

1 comment:

Average Guy said...

I think you are being very unfair to Martin Daniels.Where else would you learn secrets of trading like " This is why its ever so important to exit your trade at the correct moment".

Why didn't I think of that?
Why didn't you tell us that ?

I am now equipped to conquer the trading world.