Thread: Sample variance equation question
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Old June 26th, 2009, 03:15 PM
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the data is X_1, X_2,\ldots X_n

You're summing i from 1 to n, and it's \bar X, not X.

S^2={\sum_{i=1}^n (X_i-\bar X)^2\over n-1}

={ (X_1-\bar X)^2 + (X_2-\bar X)^2+(X_3-\bar X)^2+\cdots +(X_n-\bar X)^2 \over n-1}

OR

={\sum_{i=1}^n X^2_i-n\bar X^2\over n-1}
Last edited by matheagle; June 26th, 2009 at 11:55 PM.
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