Variance
The term variance was used to describe the square of the standard deviation by R.A.Fisher. The concept of variance is highly important in areas where it is possible to split the total into several parts, each attributable to one of the factors causing variation in their original series. Variance is denoted by σ^{2} in case of population and s2 in case of sample.
Variance is the average squared deviation from the arithmetic mean. The smaller the value of σ^{2 }the lesser the variability or greater the uniformity in the population.