And how do we denote and calculate variance for a population? Well, for a population, we'd say that the variance, we use the Greek letter sigma squared, is equal to, and you could view it as the mean of the squared distances from the population mean. But what we do is we take, for each data point, so I equal 1 all the way to N, we take that data point, subtract from it the population mean. So if you want to calculate this, you'd want to figure this out. Or that's one way to do it. We'll see there's other ways to do it, where you can kind of calculate them at the same time. But you would, the easiest or the most intuitive, calculate this first.