Results 1 to 2 of 2

Math Help - why we subtract mean while calculating covariance

  1. #1
    Newbie
    Joined
    Aug 2009
    Posts
    1

    Smile why we subtract mean while calculating covariance

    Hi all,
    First My Introduction
    My Name is Vishwasrao Salunkhe
    From India.
    My question is
    Why we subtract mean value while calculating covariance os variables.
    Thanks in advance .
    Waiting for reply.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Junior Member
    Joined
    Mar 2009
    Posts
    64
    Quote Originally Posted by vishwasrao View Post
    Hi all,
    First My Introduction
    My Name is Vishwasrao Salunkhe
    From India.
    My question is
    Why we subtract mean value while calculating covariance os variables.
    Thanks in advance .
    Waiting for reply.
    Are you asking why is

    Cov(X,Y) = E((X - E(X)) * (Y - E(Y))) ?

    This is intuitive. Let us suppose that they have positive covariance. That means we expect that an increase in X is accompanied by and increase in Y. So, if x>E(X) there is a tendency to have y>E(Y) thus making the covariance positive.

    Also, if x<E(X) we expect y<E(Y), and again Cov(X,Y)>0.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Calculating Covariance Matrix, Regression Analysis
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: November 27th 2011, 09:07 AM
  2. I can't Subtract!
    Posted in the Algebra Forum
    Replies: 4
    Last Post: October 8th 2011, 11:19 AM
  3. Help calculating covariance. thank you for your help
    Posted in the Advanced Statistics Forum
    Replies: 5
    Last Post: November 18th 2009, 12:26 AM
  4. subtract fractions
    Posted in the Algebra Forum
    Replies: 1
    Last Post: May 9th 2008, 09:00 AM
  5. subtract
    Posted in the Algebra Forum
    Replies: 3
    Last Post: September 4th 2007, 02:55 PM

Search Tags


/mathhelpforum @mathhelpforum