Variance is the variability of values of a data set from their average. The variation in a set of observations is calculated by using variance. The variance of a data set can be calculated by using formula;

Variance = summation(observations - average)

Variance is the mean of square of deviation of observation from average. To calculate the variance, we have to calculate the mean of data set. Take deviations of all the values of data set from the mean. Take square of these deviations and add all the square of deviations. Divide this total with total number of observation to get a mean. This final mean is known as variance.

Variance = summation(observations - average)

^{2}/ number of valuesVariance is the mean of square of deviation of observation from average. To calculate the variance, we have to calculate the mean of data set. Take deviations of all the values of data set from the mean. Take square of these deviations and add all the square of deviations. Divide this total with total number of observation to get a mean. This final mean is known as variance.