Results 1 to 2 of 2

Math Help - Mean and Variance

  1. #1
    Newbie
    Joined
    Dec 2008
    Posts
    6

    Mean and Variance

    Let X1 and X2 be a random sample from B(n,p). Compute the mean and the variance of X1+X2.
    Can anyone help with this one as well?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6
    Hello,
    Quote Originally Posted by Patriots326 View Post
    Let X1 and X2 be a random sample from B(n,p). Compute the mean and the variance of X1+X2.
    Can anyone help with this one as well?
    E(X1+X2)=E(X1)+E(X2)
    For the variance :
    var(X1+X2)=var(X1)+var(X2)+2 cov(X1,X2)

    If X1 and X2 are independent, then cov(X1,X2)=0


    After that, you have several other means, using probability density functions, moment generating functions, etc... But I don't know what you can use...
    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