I can assume that's pronounced Ted-eff. And what it allows us to do is give us an intuition as to why we divide by n minus one when we calculate our sample variance and why that gives us an unbiased estimate of population variance. So the way this starts off, and I encourage you to go try this out yourself, is that you can construct a distribution. It says build a population by clicking in the blue area. So here, we're actually creating a population. So we're creating, every time I click, it increases the population size. So let me just, and I'm just randomly doing this, and I encourage you to go onto this scratch pad.