# Manipulating the sample variance formula

• June 18th 2011, 06:03 AM
incblue
Manipulating the sample variance formula
Hello.

I am trying to prove the identity in red. (My failed attempt is in black)
http://img813.imageshack.us/img813/7396/ideny.png
• June 18th 2011, 06:12 AM
Re: Manipulating the sample variance formula
Quote:

Originally Posted by incblue
Hello.

I am trying to prove the identity in red. (My failed attempt is in black)
http://img813.imageshack.us/img813/7396/ideny.png

If you multiply out the numerator of the red LHS,
then use the fact that

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

the result follows.
• June 18th 2011, 06:29 AM
incblue
Re: Manipulating the sample variance formula
Quote:

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