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The formula for standard deviation must not be confused with the formula
 
The formula for standard deviation must not be confused with the formula
   −
:<math>S_{n} = \sqrt {\sum(x - \bar x) \over n - 1}</math>
+
:<math>S_{n} = \sqrt {\sum(x - \bar x)^2 \over n - 1}</math>
    
which is the formula for a [[point estimate]] of the true standard deviation from a sample size of ''n''.  As such this estimator itself has a variance which, as the formula indicates, decreases as the sample size increases.
 
which is the formula for a [[point estimate]] of the true standard deviation from a sample size of ''n''.  As such this estimator itself has a variance which, as the formula indicates, decreases as the sample size increases.
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