Substitute the value of standard deviation in the formula. X Mean of the data. X Item given in the data.
Where m is Mean N is the total number of elements or frequency of distribution.
The deviations are squared to prevent negative values from canceling out the positive values. Where s 2 Variance. With samples we use n 1 in the formula because using n would give us a biased estimate that consistently underestimates variability. Once youve done that you can compute its mean and variance using the formulas you know.