Variance
variance = (standard deviation)2 =
The units of the variance are the square of the units of the original values. For example, if the values are weights, the standard deviation might be 6 kg, but the variance would be 36 square kg. Since its units are easier to interpret, standard deviations are more easily understood measures of spread, but variances are important in advanced statistics. (An important collection of methods for analysing relationships between variables is called analysis of variance.)
Degrees of freedom (optional)
The divisor (n − 1) in the formula for the sample standard deviation is called its degrees of freedom. This is the number of 'independent pieces of information' that contribute to it.