Well, if you don't know the true proportion, the way that you estimate the standard deviation is with the standard error, which we've done in previous videos. And so this is two standard errors to the right and two standard errors to the left of our sample proportion. And our confidence interval is this entire interval going from this left point to this right point. And as we draw more samples, you can see it's not obvious, but our intervals change depending on what our actual sample proportion is, because we use our sample proportion to calculate our confidence interval, because we're assuming whoever's doing the sampling does not actually know the true population proportion. Now, what's interesting here about this simulation is that we can see what percentage of the time does our confidence interval, does it actually contain the true parameter? So let me just draw 25 samples at a time. And so you can see here that right now, 93%, for 93% of our samples, did our confidence interval actually contain our population parameter?