So it's going to be this guy divided by 10. Now, we do not know what this guy is. The only way to figure out what that guy is is to actually survey 100 million people, which would have been impossible. So to estimate the standard deviation of this, we will use our sampling standard deviation as our best estimate for the population standard deviation. So we could say, now remember, this is an estimate. We cannot come up with the exact number for this just from a sample, but we can estimate it. Because this is our best estimator for this standard deviation, and if we divide it by 10, we will have our best estimator for the standard deviation of the sampling distribution of the sampling mean.