So this thing squared. So this thing squared is what? This is x sub i, take the sum to n, i is equal to 1. 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.