From that, she would calculate her sample mean and her sample standard deviation. And from that, she would calculate this t-statistic. The way she would do that, or if they didn't tell us ahead of time what that was, they would say, okay, well we would say the t-statistic is equal to her sample mean minus the assumed mean from the null hypothesis, that's what we have over here, divided by, and this is a mouthful, our approximation of the standard error of the mean. 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?