[_D&L_]

Take the mean of your sample. (add them up, then divide by number of observations)

For each data point, subtract the data point from the mean, and square the result. (say mean is 5 and data point is 8, you subtract, you get -3, then you square it, so you get 9).

Then for each result from the previous step, add them up, and then divide by the number of data points less 1.

Variance is simply the average of the square of the distance of each data point from its mean.