How can we create a 95% interval around this, around the mean, where we are 95% sure, or construct an interval around this, where we're 95% sure that any sample from this distribution, and this is one of those samples, that there's a 95% chance that we will select from this region right over here. So we care about a 95% region right over here. So how many standard deviations do we have to go in each direction? And to do that, we just have to look at a z-table. And just remember, if we have 95% in the middle right over here, we're going to have 2.5% over here, and we're going to have 2.5% over here. We have to have 5% split between these two symmetric tails. So when we look at a z-table, we want the critical z-value that they give right over here.