The standard deviation of the sampling distribution we've seen multiple times is equal to the standard deviation of our original population divided by the square root of the number of samples. We do not know this right over here. We do not know the actual standard deviation in our population. Our best estimate of that, and that's why we call it confident, we're confident that the real population proportion is going to be in this interval. We're confident, but we're not 100% sure because we're going to estimate this over here. If we're estimating this, we're really estimating that over there. If this can be estimated, it's going to be estimated by this sample standard deviation.