Results 1 to 4 of 4

Math Help - pdf and variance

  1. #1
    Junior Member
    Joined
    Sep 2009
    Posts
    42

    pdf and variance

    Solved
    Last edited by dynas7y; March 31st 2010 at 04:46 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member Anonymous1's Avatar
    Joined
    Nov 2009
    From
    Big Red, NY
    Posts
    517
    Thanks
    1
    []EDIT[]The interval was unspecified. Please check the interval on which the density is defined and put it in place of [a,b]

    E[Y]= \int_{a}^{b} y \times 3(1-y)^2 dy

    E[Y^2]= \int_{a}^{b} y^2 \times 3(1-y)^2 dy

    Also, Var(Y) = E[Y^2] - (E[Y])^2

    and, Var(W) = 25Var(Y)

    Use:

    http://integrals.wolfram.com/index.jsp

    to speed up your integration.
    Anonymous
    Last edited by Anonymous1; March 16th 2010 at 05:45 PM.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor matheagle's Avatar
    Joined
    Feb 2009
    Posts
    2,763
    Thanks
    5
    clearly the region isn't all of R^1 so that integration is incorrect

    NEXT comment, the region is most likely (0,1) and that means this is a Beta(1,3)
    you can look up it's variance in that case.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member Anonymous1's Avatar
    Joined
    Nov 2009
    From
    Big Red, NY
    Posts
    517
    Thanks
    1
    Yeah, it was unspecified so I just kinda went to default. Thanks for catching that.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Help with variance
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: September 3rd 2011, 01:53 AM
  2. variance of the sample variance
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: February 8th 2011, 08:35 PM
  3. How to get new variance given old variance and average
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: November 23rd 2010, 05:39 AM
  4. Variance Help
    Posted in the Statistics Forum
    Replies: 2
    Last Post: August 23rd 2009, 01:22 PM
  5. Variance of the population variance.
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: November 10th 2008, 09:07 AM

Search Tags


/mathhelpforum @mathhelpforum