Results 1 to 4 of 4

Math Help - Expected Value

  1. #1
    Senior Member Twig's Avatar
    Joined
    Mar 2008
    From
    Gothenburg
    Posts
    396

    Expected Value

    Hi!

    Problem: A die is rolled twice. Let X denote the sum of the two numbers that turn up, and Y the difference of the numbers (specifically, the number on the first roll minus the number on the second roll). Show that

    E(XY)=E(X)\cdot E(Y)

    Are X and Y independant?

    Thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by Twig View Post
    Hi!

    Problem: A die is rolled twice. Let X denote the sum of the two numbers that turn up, and Y the difference of the numbers (specifically, the number on the first roll minus the number on the second roll). Show that

    E(XY)=E(X)\cdot E(Y)

    Are X and Y independant?

    Thanks
    Use this table: Dice table

    to get the distribution for X, Y and XY. Then calculate the required expectations.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Senior Member Twig's Avatar
    Joined
    Mar 2008
    From
    Gothenburg
    Posts
    396
    Thank you
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member Focus's Avatar
    Joined
    Aug 2009
    Posts
    228
    Quote Originally Posted by Twig View Post
    Are X and Y independant?
    .

    What is the probability that the difference is 11? If I told you they sum up to 2, what is the probability that they have difference 11?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Expected Value
    Posted in the Statistics Forum
    Replies: 1
    Last Post: April 25th 2011, 04:51 PM
  2. Expected value/ st dev/var
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: September 30th 2010, 03:55 AM
  3. Expected Value
    Posted in the Advanced Statistics Forum
    Replies: 9
    Last Post: September 20th 2010, 12:52 AM
  4. Expected Value
    Posted in the Statistics Forum
    Replies: 3
    Last Post: April 28th 2009, 05:05 PM
  5. expected value
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: January 16th 2009, 09:51 AM

Search Tags


/mathhelpforum @mathhelpforum