And actually, you can calculate other things like a sample standard deviation. But now you have an issue. You say, well, ideally, I would use a Z statistic. And you could if you were able to say, well, I could take the difference between my sample mean and the assumed mean in the null hypothesis. So that would be this right over here. That's what that zero means, the assumed mean from the null hypothesis. And I would then divide by the standard error of the mean, which is another way of saying the standard deviation of the sampling distribution of the sample mean.