Results 1 to 4 of 4

Math Help - Expected value problem

  1. #1
    Junior Member
    Joined
    Oct 2008
    Posts
    70

    Expected value problem

    Hey i'm having a little trouble with expected value so i don't really understand how to do this problem:

    Assume that N people check their hats and the hats are handed back to them at random. Let X_j = 1 if the jth person gets his or her hat and 0 otherwise. Find E(X_j) and E(X_j * X_k) for j not equal to k. Are X_j and X_k independent?

    Thanks!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor matheagle's Avatar
    Joined
    Feb 2009
    Posts
    2,763
    Thanks
    5
    since (1)(1)1 =1 and (0)(0)=0=(0)(1)

    X_j=1 if this person gets his/her hat 0 otherwise
    so E(X_j)=p(J th person get their hat)

    and X_j * X_k= 1 iff both get their hats

    so E(X_j * X_k)=P(both the j th and k th people get their hats)
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Oct 2008
    Posts
    70
    thank you!
    so is p(X_j) = j*(j-1)! ?
    but I'm not sure how to find p(X_k) or p(X_j * X_k)...
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor matheagle's Avatar
    Joined
    Feb 2009
    Posts
    2,763
    Thanks
    5
    probabilities do not exceed 1
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Expected value problem
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: October 25th 2010, 10:02 PM
  2. An Expected Value Problem
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: June 5th 2010, 10:28 PM
  3. sorry one more expected value problem
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: July 19th 2009, 10:18 PM
  4. Help with expected value problem
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: September 11th 2008, 05:32 AM
  5. Expected value Problem
    Posted in the Advanced Statistics Forum
    Replies: 5
    Last Post: May 25th 2007, 02:04 PM

Search Tags


/mathhelpforum @mathhelpforum