So let's say I want to figure out the probability. I'm going to flip a coin eight times, and it's a fair coin. And I want to figure out the probability of getting exactly three out of eight heads. So I say three eight heads. But three of my flips are going to be heads, and the rest are going to be tails. So how do I think about that? Well, let's go back to one of the early definitions we use for probability.