


Description 



Variance: A measure of how spread out a set of data is. 
The variance provides information about how spread out a set of data is. It is calculated in three steps. First, find the difference between each member of the data set and the mean and square the difference. Second, add up all of the squares of the differences. Third, divide that sum by the number of members minus 1 in the data set. This gives the unbiased estimate for the variance. However if we divide the sum by the number of members in the data set, then we find a biased estimate for the variance.
For example, for the the data set: 1, 2, 3.
The biased variance is
In summation, the formula looks like
The unbiased variance is
In summation, the formula looks like


