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Variance and Convariance

  1. Sep 6, 2013 #1
    Could someone please explain it to me what is the difference between Variance and Covariance?
  2. jcsd
  3. Sep 6, 2013 #2


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    Science Advisor

    "Variance" applies to a single random variable. "Covariance" applies to two or more related random variables.
  4. Sep 6, 2013 #3
    Could you please give me an example?
  5. Sep 6, 2013 #4


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    Let X and Y be random variables.

    var(X) = E(X2) - E(X)2

    cov(XY) = E(XY) - E(X)E(Y)

    E(..) means average.
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