Now, you'll see this in a probability or statistics class, and people might memorize this thing, it seems like this kind of daunting thing. I'll just tell you right now, the whole reason why I just showed this to you is so that you could connect it with what you might see in your textbook, or what you might see in a class, or when you see this type of formula, you see that it's not coming out of, it's not some type of voodoo magic, but I will tell you that for me, personally, I never use this formula. I always reason it through, because if you just memorize the formula, you're always going to wait, does this formula apply there? What's n, what's r? But if you reason it through, it comes out of straight logic. You don't have to memorize anything, you don't feel like you're just memorizing without understanding, you're just using your deductive reasoning, your logic. And that's especially valuable, because as we'll see, not every scenario is going to fit so cleanly into what we did.