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Homework Help: Expected value - Statistics question about E(X) and E(X^2) in a beta distribution

  1. Aug 9, 2008 #1
    1. The problem statement, all variables and given/known data

    The actual question I'm working on is to find the Method of moments for [tex] \theta [/tex] for a beta distribution where the parameters are m = n= [tex] \theta [/tex]

    2. Relevant equations

    What I need help with is to get started, I know that E(X)=1/2 for this question so that it does not depend on [tex] \theta [/tex] My actual problem is that I need to calculate E(X^2) and I can't find any info on how to calculat E(X^2) for a beta distribution, I know the answer is ([tex] \theta [/tex] +1)/(2(2[tex] \theta [/tex] +1))

    3. The attempt at a solution

    I found a formula on Wiki for Variance of a beta distribution and thought i'd try it, although I know that variance is E(X)^2 - E(X^2) anyway I ended up with 1/(4(2[tex] \theta [/tex] +1)) which was close, but not it.... Once I find E(X^2) I should be able to answer the actual question I'm working on

    Thanks :)
  2. jcsd
  3. Aug 9, 2008 #2
    ahh dont worry I've figured it out, I've got E(X) and I've got Var(X) so I'll find E(X^2) using that formula for variance... thanks anyway
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