I've just taken the sum of each of these things, the sum of the difference between each data point and the population mean and squared it. If I really want to get the way I figured out this variance right over here, I have to divide the whole thing by the number of data points we have. So this might seem very daunting and very intimidating. But all it says is, take each of your data points. Well, one, it says, figure out your population mean. Figure that out first. And then from each data point in your population, subtract out that population mean, square it, take the sum of all of those things, and then just divide by the number of data points you have.