November 05, 2010

Why normal is unusual

A concentration of pharmacologistsThe Swedish blog has an excellent little post about normality. It shows that being different from the norm is quite normal. The argument has been made before, but it is worth repeating.

If we assume the following rather modest simplifications:

  1. There are about 200 ways of being different, i.e. being part of a protoypical minority such as being diabetic, gay, adopted, scientologist etc.
  2. Each difference minority is 2% of the population. Obviously this is just approximate, but seems roughly representative (In Sweden diabetics are 3.9%, homosexuals ~3%, foreign adopted 0.7%, Muslims 1.2%, scientologists 0.5%)
  3. Differences are uncorrelated.

One can quibble a bit with each of these assumptions, but mild modifications do not change the conclusion much.

Given this, the probability of being normal (in the sense of not being different along any of these 200 dimensions) is 0.98200=1.8%. So normals are a rarer than the other minorities!

True normality is hence so rare that it makes you a member of a very small and odd minority.

Posted by Anders3 at November 5, 2010 04:05 PM