I'm just saying the standard deviation of that distribution. So what is the standard deviation of that distribution? We actually calculated it in the last video, and I'll recalculate it here. The standard deviation of our distribution, of the difference of the mean, the distribution of the difference of the sample means, is going to be equal to the square root of the variance of our first population. Now the variance of our first population, we don't know it, but we can estimate it with our sample standard deviation. If you take your sample standard deviation, 4.67, and you square it, you get your sample variance. So this is the variance, this is our best estimate, of the variance of the population.