I couldn't make this as fun as the Mean Machine, in fact it is basically all numbers. (If anyone can think of how to make it more fun, please say!)
Here it is: Standard Deviation Calculator
Is it right?
"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman
Bug: It almost looks like you got a pentium bug.
Enter 2, 13, 13, 7, 9
The last difference is 0.1999999999 when it should be 0.2
It copies over (expectedly) to the square of the difference.
"In the real world, this would be a problem. But in mathematics, we can just define a place where this problem doesn't exist. So we'll go ahead and do that now..."