Calculate Standard Deviation

Clip, 3

.sk

.s is the standard deviation, k parses the input in the form {1,2,3}.

Nice, Mathematica has a built-in StandardDevi... oh... that computes the sample standard deviation, not the population standard deviation.

But what if we use Variance... oh... same deal.

But there is yet another related built-in:

CentralMoment[#,2]^.5&

Yay. :)

This also works for 22 bytes:

Mean[(#-Mean@#)^2]^.5&

And this for 27:

N@RootMeanSquare[#-Mean@#]&

g=@(a)std(a,1)

Try it on ideone.