Results 1 to 2 of 2

Math Help - Sigma (standard deviation) properties homework question - assistance requested

  1. #1
    Newbie
    Joined
    Jan 2011
    Posts
    15

    Sigma (standard deviation) properties homework question - assistance requested

    ImageShack® - Online Photo and Video Hosting

    Is there any way of doing this problem without using any identities involving covariance? (I don't know what that is).

    What is the answer this problem anyway?

    Possible answers: 25/4, 5/2, 9/2, 3/sqrt(2), 1/2
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor matheagle's Avatar
    Joined
    Feb 2009
    Posts
    2,763
    Thanks
    5
    Let W=X+Y

    P(W=-2)=.5=P(W=3)

    So E(W)=.5 E(W^2)=13/2

    the variance of W is 6.5-.25
    now take the square root.....5/2

    No need to obtain the joint distribution of X and Y, just find the distribution of W.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. 3-Sigma and Standard Deviation
    Posted in the Statistics Forum
    Replies: 4
    Last Post: November 15th 2010, 12:17 AM
  2. Standard deviation question
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: April 13th 2010, 01:27 PM
  3. Standard Deviation question
    Posted in the Statistics Forum
    Replies: 1
    Last Post: November 23rd 2009, 10:34 PM
  4. Replies: 2
    Last Post: May 7th 2009, 11:29 AM
  5. question about standard deviation
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: October 7th 2005, 05:16 PM

Search Tags


/mathhelpforum @mathhelpforum