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QM - variance

  1. Sep 23, 2007 #1
    1. The problem statement, all variables and given/known data

    Compute the variance of the random variable X given by

    [tex]V(X) = \sqrt{E((X-E(X))^2)}[/tex]
    where E(X) is the expectation value of random variable X

    2. Relevant equations

    Hint: Use parameter differentiation

    3. The attempt at a solution

    I have no idea what to do here. I've never taken a class in probability and I have never heard of parameter differentiation. I've seen definitions of variance the same as above minus the square root sign so I'm confused.
    Last edited: Sep 23, 2007
  2. jcsd
  3. Sep 23, 2007 #2


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    look at "Computational formula for variance"

    hmm you should have no square root; the formula you have is the standard devation S(x)

    S(x) = (V(x))^(1/2)

    At least what I know of statistics.

    Use that E is linear operator (E : expectation value)

    But I must say that it is hard so see what is meant by the problem..
    Last edited: Sep 23, 2007
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