Okay, so let's give you a homework problem that will help you prepare for the test questions on the Pythagorean Theorem. Okay, so in the file Pythagorean Football.xlsx we've got three years of NFL stats, we've got wins, losses, and ties, and there are ties in the NFL, although albeit rare. So we're going to count it by is half a win. So what I want you to do is find the best Pythagorean exponent for NFL. And then figure out if you were an average NFL team playing an average NFL opponent, how many more points would you have to score to win one more game? Now in the NFL, as you know there, are 16 regular season games. I'm taking this as the Deflategate Report came out and we will have some discussion of Deflategate in the course. And we'll have some statistical analysis of the suggest that the Patriots were doing something funny to the footballs and it looks like they probably were. So, that'll be interesting. So, counting a tie as half a win, what I'd like you to do is do the MAD on predicting the number of wins, okay? Now a little trick here on a function, okay, so you're going to want to figure out the absolute error of the scoring ratio of the predicted wins here. And you want to copy the formula all the way down but you see these blanks here? That's really annoying. So if you want to copy a formula down, okay, and they're going to be blanks, you're going to get an error message. If I would just say, points for divided by points against. So this is points divided by points against. Now if I were to copy that down, see? I get these divide by 0 errors because there's nothing there. Now that's a pain. So Excel embedded a nice function for that. And so you should be using these functions in your job as well as in the course. But it's called IFERROR. And so if error works as follows. You put in a formula, and if it works, the formula works. Otherwise, you put in an error message or something. Here we just want a blank, because Excel ignore blanks in calculations. So in other words, if I want to compute the scoring ratio, I could say IFERROR, okay? And I could say points for divided by points against. And then, just put quote, double quote, double quote, is a blank. Things in Excel have to be enclosed in quotes if they're going to be text. Now that I could just copy all the way down. And again, in the calculations, the blanks'll be ignored. Don't put a zero in, they're not ignored. See when I copy that down in this row, the IFERROR takes over because you can't divide this stuff and it becomes a blank instead the divide by zero error. So I think you'll find that IFERROR function useful in doing homework and test questions and just in your general everyday life. Okay, that's it for this video. Do this problem and you should be ready to take test question one and two which involve Pythagorean exponent for the NBA.