 Enter the star of our show, the parameter. In statistics, the parameter refers to a summary measure of a population. Now, you are deeply, desperately, excited by that population, by those trees. And now I'm going to summarize for you everything you care about. Be still, your little heart. You are excited by this number. And it turns out that here, the true average height of all the trees, the parameter, is 21.1 meters. But it is Saturday morning, and you are standing in this clearing right here. You have measured no trees yet, but you are desperately excited by this number. What's it going to take to get it? What would you have to do? Measure all the trees. Measure all the trees perfectly with no mistakes, correct? And then once you've got that data set, all you've got to do is just take the average and you are done. And that is descriptive analytics. You know your answer with certainty. Nothing special or extra, no p-values or confidence intervals. Just report the answer. Now, I don't know about you guys. But I live in New York by choice, as far away from trees as possible. And so if I'm faced with the idea that I must go and perfectly measure all of those cursed trees on my weekend, I begin thinking statistically. I'm going to be lazy, in other words. I say to myself, well, I would love to know that number. And I agree. The only way to actually know that number, to have it with certainty, is to measure all of those trees. I don't want to. So maybe I don't need to know it. Maybe I can instead make do with measuring some, not all of the trees, and forming a reasonable belief for best guess about this number that's good enough for government work. And when I'm thinking that way, I'm thinking like a statistic. I'm not going to have all the information. Now I'm not going to know that number. But from my partial information and less effort than measuring all the trees, maybe I can still get something useful that I can use to make a reasonable, real-world decision. So that is our game here. That's the entire game that we're about.