And so that's why instead we do a t-statistic, in which case we take the difference between our sample mean and our assumed population mean, the population parameter, and we try to estimate this. And we estimate that with our sample standard deviation divided by the square root of our sample size. And so if you're inspired, I encourage you, even if you're not inspired, I encourage you to pause this video and try to calculate this t-statistic. Well, this is going to be equal to, let's see, our sample mean is four minus our assumed mean is five, our assumed population mean is five. Our sample standard deviation is two. All of that over the square root of the sample size, all of that over the square root of 25. So this is going to be equal, our numerator is negative one.