Results 1 to 3 of 3

Math Help - X~Exp(x,θ) prove or disprove that E[x^2]=2 (θ)^2

  1. #1
    Member
    Joined
    Jan 2009
    From
    Kingston, PA
    Posts
    96

    X~Exp(x,θ) prove or disprove that E[x^2]=2 (θ)^2

    X~Exp(x,θ) prove or disprove that E[x^2]=2 (θ)^2.

    I know the pdf and how to find E[x^2] but not sure how to show it equals (θ)^2.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor harish21's Avatar
    Joined
    Feb 2010
    From
    Dirty South
    Posts
    1,036
    Thanks
    10
    Quote Originally Posted by nikie1o2 View Post
    X~Exp(x,θ) prove or disprove that E[x^2]=2 (θ)^2 NOOOO!!!! I think you were trying to write 2 (θ)^-2.

    I know the pdf and how to find E[x^2] but not sure how to show it equals (θ)^2.
    For an exponential distribution, E[X^2]=2{\theta}^{-2}=\dfrac{2}{\theta^2}

    E[X^2]= \displaystyle \int_0^{\infty} x^2\; \theta\;e^{-\theta{x}}\;dx

    integrate by parts..
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Jan 2009
    From
    Kingston, PA
    Posts
    96
    Ah Ha! well i was asked to prove or disprove this so i presume the claim is false then ! I'll have to do an counter example
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. prove or disprove
    Posted in the Differential Geometry Forum
    Replies: 2
    Last Post: April 19th 2010, 03:16 PM
  2. Prove or disprove that (ac,b) =1
    Posted in the Advanced Algebra Forum
    Replies: 4
    Last Post: March 8th 2010, 05:07 PM
  3. How do I prove/disprove this?
    Posted in the Number Theory Forum
    Replies: 2
    Last Post: March 7th 2010, 06:00 AM
  4. Prove or disprove help
    Posted in the Algebra Forum
    Replies: 3
    Last Post: March 27th 2008, 09:06 PM
  5. Help me to prove or disprove this:
    Posted in the Discrete Math Forum
    Replies: 5
    Last Post: January 17th 2008, 06:41 PM

Search Tags


/mathhelpforum @mathhelpforum