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Thread: Why n-1 when estimating population variance from a sample?

  1. #1
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    Why n-1 when estimating population variance from a sample?

    The formula for variance (and standard dev) uses n. Why is n-1 used when estimating pop variance from a sample? I realise that using n-1 (in the denominator) results in a larger value. But why n-1 and not say, n-2? Is there a simple explanation?
    Also, doesn't our estimate also depend on how large n (sample size) is compared to pop size N? Should we use a "correction factor" similar to that used for confidence intervals?
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  2. #2
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    Re: Why n-1 when estimating population variance from a sample?

    I believe using $n-1$ makes the variance estimate unbiased.
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