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Who can tell me something about degree of freedom in statistic?

  1. Apr 22, 2012 #1
    being stuck by standard deviation, I just can't understand the difference between n and n-1.
    who can give me some concrete examples?
    thank you!
     
  2. jcsd
  3. Apr 22, 2012 #2

    chiro

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    Science Advisor

    Are you referring to the estimated standard deviation vs the actual standard deviation?

    If so the reason is because the (n-1) term has to do with the fact that dividing by (n-1) instead of n will result in an unbiased point estimator of the variance and hence standard deviation.

    Basically for unbiased estimators you have to show that E[σest2] = E[σ2] and what this ends up doing is forcing you to use the (n-1) in terms of n.
     
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