So let's draw it. Let's draw it like this. Well, there's a couple of things we immediately know about z. And we kind of came up with this in the last video. So the mean of z, instead of writing z, I'm just going to write the mean of x. Let me do that same shade of green. The mean of x bar, which is the mean of x minus, or a sample from the sampling distribution of x, or the sample mean of x, minus the sample mean of y.