testing header
Math Goodies is a free math help portal for students, teachers, and parents.
Free Math
Interactive Math Goodies Software

Buy Math Goodies Software
testing left nav
Math Forums @ Math Goodies
Math Forums @ Math Goodies
Home | Profile | Active Topics | Members | Search | FAQ
Save Password
Forgot your Password?

 All Forums
 Homework Help Forums
 Probability and Statistics
 Proof of Sample Variance Equation
 New Topic  Topic Locked
 Printer Friendly
Author Previous Topic Topic Next Topic  

New Member

2 Posts

Posted - 09/25/2007 :  09:54:26  Show Profile
I have been trying to prove that one form of the equation for sample variance,x-((x)n) = (x-mean), another form of the same equation.

So far, given the definition of mean being xn , I now have x-((x)n) = (x-((x)n))

I have been looking online and have not found what to do after this step. Is there a way to separate the right half of the equation into the two parts separated by the subtraction on the left side? Or how can you change the n that is on the right side into the n present on the left?
Go to Top of Page

Advanced Member

1001 Posts

Posted - 09/25/2007 :  10:40:42  Show Profile
It may help to know the specific words "Machine Formula".


Also, please check your notation. You appear to have some exponents in the wrong places.
Go to Top of Page

New Member

2 Posts

Posted - 09/26/2007 :  06:37:54  Show Profile
You were right, the equation is x-((x)n)= (x-mean)

I finally found the proof. It is basically working with the principle that mean=(x)n. Also, that mean and x = nmean and nx, respectively. You can factor the (x-mean) into a trinomial, then, by reworking the two last factors using the definitions above, combine the second and third terms because they are like terms.

Thank you so much for your help and the website links!
Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Topic Locked
 Printer Friendly
Jump To:
Math Forums @ Math Goodies © 2000-2004 Snitz Communications Go To Top Of Page
This page was generated in 0.04 seconds. Snitz Forums 2000
testing footer
About Us | Contact Us | Advertise with Us | Facebook | Blog | Recommend This Page

Copyright © 1998-2014 Mrs. Glosser's Math Goodies. All Rights Reserved.

A Hotchalk/Glam Partner Site - Last Modified 18 Dec 2014