You're going to square this thing, and then you're going to divide it by, we squared, right? You divide it by n squared. And this might seem like a more, out of all of them, this is actually seems like the simplest formula for me, where you essentially just take, if you know the mean of your population, you just say, OK, my mean is whatever, and I can just square that, and just put that aside for a second. But first, I can just take each of the numbers, square them, and then sum them up, and divide by the number of numbers I have. I don't know if I wrote, no, I've erased the last set of numbers, but we could show you that you'll get to the same variance. So to me, this is almost the simplest formula. But this one's even faster in a lot of ways, because you don't really have to even calculate the mean ahead of time.