Results 1 to 2 of 2
Like Tree1Thanks
  • 1 Post By mr fantastic

Math Help - Calculating E(X) and V (X)

  1. #1
    Newbie
    Joined
    Aug 2009
    Posts
    20
    Thanks
    1

    Calculating E(X) and V (X)

    Let X be a random variable taking values in the positive integers, with probability mass function of the form:

    pX (k) = 2/3^(−k)


    Does E(X) and V (X) exist for this pmf? and how should I calculate them? or why they are not exist?
    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 sweetadam View Post
    Let X be a random variable taking values in the positive integers, with probability mass function of the form:

    pX (k) = 2/3^(−k)


    Does E(X) and V (X) exist for this pmf? and how should I calculate them? or why they are not exist?
    Does E(X) = \sum_{k = 1}^{+\infty} \frac{2k}{3^k} converge?

    Does E(X^2) = \sum_{k = 1}^{+\infty} \frac{2k^2}{3^k} converge?
    Thanks from sweetadam
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Calculating mean
    Posted in the Statistics Forum
    Replies: 1
    Last Post: April 16th 2011, 05:27 AM
  2. Calculating APR
    Posted in the Business Math Forum
    Replies: 2
    Last Post: January 19th 2011, 07:09 PM
  3. Calculating y'
    Posted in the Calculus Forum
    Replies: 5
    Last Post: January 3rd 2010, 01:34 PM
  4. calculating P(X>=Y)
    Posted in the Statistics Forum
    Replies: 2
    Last Post: February 4th 2009, 12:30 PM
  5. calculating p-value
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: July 20th 2008, 09:06 PM

Search Tags


/mathhelpforum @mathhelpforum