Picking An NCAA Tournament Bracket With Pythag And Log5

[Note by Joel Hollingsworth, 03/12/12 9:10 PM EDT ] You can find the 2012 version of this post here.

Three years ago, I filled out one of my NCAA brackets using nothing but team pythags. The thing actually placed second in the Rocky Top Talk Bracket Challenge, so, after a year of complete and total slacking, I did it again last year, and the thing finished third. I also filled out a bracket using upset profiling developed by CBS's Peter Tiernan. It did really well in the first round but ended up 38th out of 40 in the final standings, so so much for the idea of magic formula to pick upsets.

Anyway, I figured we'd wind the pythag bracket up again this year and see if it can show in three of three years. As a refresher, here's the explanation I offered back in 2008:

After staring at A Sea of Blue's post setting forth the odds for each of the NCAA Tournament teams to win it all for a half an hour, I concluded: whoa, numbers. But once I recovered, I thought it would be interesting to see how each game of the bracket plays out using Ken Pomeroy's data. Below is the NCAA Tournament bracket, with each region on top of each other (as opposed to the four regions facing each other in groups of two) because who among us has a 34" computer monitor? The play-in game is on top and the final four is on the bottom. The four digit number immediately next to each team is that team's pythag, and the percentages next to the pythags are those teams' respective "chances of winning" that game. For instance, based on their respective pythags, Mt. St. Mary's should beat Coppin State 88.85% of the time and so we'll consider them the winner and move them forward to play North Carolina. Yes, you can get the same result by looking only at the teams' respective pythags, but I think the percentages give you a better feel for how those numbers might play out on the court.

A couple of pre-post observations from Hooper:

Pythag uses "pace-neutral" weighting, which means it compares the ratios of point differentials but not the actual values of point differentials. For example, a team that averages 80 pts. for and 70 pts. against looks identical to a team that averages 64 pts. for and 56 pts. against. KenPom does this so he doesn't have to worry about how many possessions a team normally has in a game. But that does make a big difference in the play of a game. So you lose valuable data at the start. This is normal for every numerical method, but it's good to know what is being lost. What this means is that Kansas has had the best pts. for / pts. against performance per possession in the league. But we don't know how many possessions is ideal for Kansas, or even if it makes a difference.

We also don't know the uncertainty. For example, if a team has a "70% chance of winning", does that mean 70% +/- 15%, or 70% + / 5%? If it's the first, then it's not unreasonable to see an upset. If it's the second, then an upset would be a tremendous shocker. We don't have a feel for the significance of a point spread, in other words.

If anyone wants to update the table to account for any of that, have at it. Start here, then read this [link dead], then read this. In the meantime, though, have a look at the table below, all dressed up in pretty Easter pastels for your enjoyment.

Oh, and one more thing: I've entered this bracket into the RTT ESPN Tournament Challenge so we can keep track of how well it does. If anyone calls Ken Pom an idiot because this entry doesn't finish in the top spot, I will personally come over to his house, pull out his toenails with a pair of pliers one by one every hour on the hour, write "no, you're the idiot" on each one in pink fingernail polish, and feed them to him. And Jackson the Mule will be right behind me to finish you off.

Okay, so that was three years ago. Here's this year's pythag bracket picks, subject as always to over-tired operator error:

2011 pythag bracket round 1

2011 pythag bracket east regional

2011 pythag bracket west regional

2011 pythag bracket southwest regional

2011 pythag bracket southeast regional

2011 pythag bracket final four

Nothing terribly exciting in there with the four #1 seeds all advancing and the #1 seed overall taking home the trophy. The pythag may not surprise, but in two of two years we've done this, it doesn't play around, either. We'll see.

Don't forget to play the RTT Bracket Contest by entering your bracket in the Rocky Top Talk bracket contest group at ESPN.

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