And the way we get that approximation, we take our sample standard deviation and divide it by the square root of our sample size. Well, they've calculated this ahead of time for us. This is equal to negative 1.9. And so if we think about a t-distribution, I'll try to hand-draw a rough t-distribution really fast, and if this is the mean of the t-distribution, what we are curious about, because our alternative hypothesis is that the mean is less than 18, so what we care about is, well, what is the probability of getting a t-value that is more than 1.9 below the mean? So this right over here, negative 1.9. So it's this area right there. And so I'm gonna do this with a TI-84, at least an emulator of a TI-84, and all we have to do is we would go to second distribution and then I would use the t-cumulative distribution function.