### Variance

The dispersion of the data from the mean. Variance measures the sum of the difference (deviation) between each observation and the mean. We have to square each of these deviations to keep them as positive values, if we didn’t the variance would always sum to zero.

In Excel, VAR.P is the function to use if you have the full population available alternatively VAR.S or VAR will estimate the variance if you just have a sample.