Khan/khan-exercises — pull request #16009 by elyip (2012-03-12 05:39:14+00:00)
Title: Add  three New Statistics Exercises

I submitted three statistics exercises:
(1) Alternate variance formula,
(2) Binomial distribution and
(3) Poisson distribution
I included a simple statistics calculator with these exercises.

This is my first pull request; I am looking forward to your feedback.