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. You can just say, OK, for each xi, I just perform this operation, and then I divide by n squared or n accordingly, and I'll also get to the variance. So you don't have to do this calculation before you figure out the whole variance. But anyway, I thought it would be instructive and hopefully give you a little bit more intuition behind the algebra dealing with sigma notation, if we kind of worked out these other ways to write variances.