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Homework Help: Expectation value of the expectation value

  1. Sep 28, 2011 #1
    1. The problem statement, all variables and given/known data
    The expectation value of the position observable x is <x> = ∫ψ*xψdx. The expectation value of the expectation value, <<x>>=<x>, is still the expectation value...why?

    2. Relevant equations

    3. The attempt at a solution

    All I can think of is that the expectation value is essentially an average, and the average of an average is the original average.

    i.e.) A={2,8} The average is (2+8)/2 = {5}
    The average of {5} = {5}.
  2. jcsd
  3. Sep 28, 2011 #2


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    Science Advisor
    Homework Helper

    The expectation value is a number which <comes out> of the integral of the expectation value of the the expectation value.
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