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Statistics Formula: Where did it come from?

  1. Aug 16, 2005 #1
    Last edited by a moderator: Apr 21, 2017
  2. jcsd
  3. Aug 16, 2005 #2


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    Science Advisor

    This may not answer your question completely. However the mathematical expectation (theoretical average) of s2 is the theoretical variance of the statistical average.
  4. Aug 16, 2005 #3


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    This will not be completely answer it but
    In statistics the idea is to get a picture of how lots of numbers act by using a few numbers. The first statistic often used is the mean
    If our data has mean 0 we might like to know are all the numbers zero, most, maybe half are 1000000000 and half -1000000000. We want an idea of spreadoutness. so we consider
    but it is zero we cure that with
    but we are using n numbers like n+1 (mean(x) depends on x hence is not its own number)
    so we do
    but it is squarey so
    which is the standard deviation we know and love
  5. Aug 16, 2005 #4
    That helps thx. I now get most of the formula except why is it (n-1)?
  6. Aug 16, 2005 #5
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