These are just the numbers that you have to essentially memorize. And if you have a calculator or normal distribution table, you don't have to do this. But sometimes in class, or people want you to estimate percentages, and so it's good to do, you can impress people if you can do this in your head. So let's see if we can use the empirical rule to answer this question, the area under the bell curve all the way up to 1, or everything to the left of 1. So the empirical rule tells us that this middle area between one standard deviation to the left and one standard deviation to the right, that right there is 68%. We saw that in the previous video as well. That's what the empirical rule tells us.