# Math Help - Manipulating the sample variance formula

1. ## Manipulating the sample variance formula

Hello.

I am trying to prove the identity in red. (My failed attempt is in black)

2. ## Re: Manipulating the sample variance formula

Originally Posted by incblue
Hello.

I am trying to prove the identity in red. (My failed attempt is in black)
If you multiply out the numerator of the red LHS,
then use the fact that

$\sum{x_i}=n(mean)$

the result follows.

3. ## Re: Manipulating the sample variance formula

$\sum{x_i}=n(mean)$