Tuesday, August 24, 2010

Luckiest Big Ten Football Team

The Iowa Hawkeyes were notorious last year for their multiple fourth quarter comebacks. Some people call it clutch, but in sports statistics we call it luck. This would make the Hawks a very lucky team. Last night though Alex Potter and Andy Meisner tried to tell me Northwestern (jNU) was the luckiest team in the Big Ten. So who is it really?

The best way to find a team's luck is to compare it's point differential to it's wins. If a team scores more points than it's opponents do, usually it wins most of it's games. The Big Ten has data for the conference season. By graphing both Big Ten wins and Big Ten point differential, then adding a trendline, we can find each point gained is about 1/30th of a win, and a point differential of 0 is worth roughly 4 wins. Then we can use the team's point differential to predict it's wins (Illinois scored 58 points less then it's Big Ten opponents, meaning it should've won 2.07 games. It won two, so that's pretty good.)

Just the Big Ten schedule takes out a couple of games though, so I also did the comparison for the whole schedule (called the simple rating). On top of that, I used last year's power rankings and opponent strength to predict wins and compared it (called the complex rating). The following table is the results (positive means a team was lucky, won more than it should've).

Big Ten Simple Complex
Ohio State -1.038 -1.426 -0.06
Iowa 0.497 2.039 2.02
Penn State -1.17 -1.487 0.124
Wisconsin -0.402 0.15 0.62
Northwestern 1.7 1.555 0.978
Michigan State 0.566 -1.211 -1.775
Purdue 0.8 0.013 -0.357
Minnesota 0.167 1.273 0.739
Illinois -0.065 -0.372 -1.152
Michigan -0.031 -1.09 -1.402
Indiana -1.032 0.627 -0.405

What does that mean? Yes, Northwestern won more games than it should've (probably just 1 more), so they were lucky. But the luckiest team in the Big Ten was definitely the Iowa Hawkeyes, who won about 2 games more than they should've. Which bodes poorly for the future because luck doesn't carry over years so the Hawks might not live up to the hype this year. Going the other way are the Michigan teams, both of which were very unlucky last year. Here's hoping the Hawks go with skill instead of luck this year.


  1. I take issue with your method of determining luck for the following reasons,

    Some teams run up the score, others do not. Florida, keeping Tim Tebow in until the fourth quarter so that he can score 9000 touchdowns would have a higher point differential than a team like iowa who takes starters out if they are comfortably in the lead.

    Strength of schedule doesn't seem to play much of a role. Teams that play an easier schedule will probably win by more than teams that play other good teams. This does not inherently mean that teams with a tougher schedule are more lucky

    Defensive minded teams will almost never blow someone out. Iowa was never really in danger of losing the Minnesota game, but we only won by 12. Offensive teams will blow people out. This isn't a difference in luck, rather it is a difference in strategy.

    Most people will probably agree that Iowa's luckiest game last year was against Indiana. Sash's pick six, that one receiver somehow failing to get a foot down for Indiana, Indiana's inability to drain the clock. However we won that by 20 points. Georgia Tech we manhandled, but won that by less than two touchdowns. Clearly Indiana was the luckier game, but under your system of evaluation that wouldn't come through.

    Luck is not how badly you beat someone. Luck is a fumble bouncing into your hands, or an opposing receiver dropping a sure touchdown, or injuring a team's star quarterback and ruining their perfect season. Purdue wasn't "lucky" to beat Ohio State. They just beat them. This is why your measurement is wrong.

  2. It's true that running up the score would make you appear to have worse luck a little bit, and that defensive teams have a disadvantage in point differential. But those are actually accounted for in my rating. A 12-0 win is roughly equivalent to a 60-35 win. Also, once a team is ahead by a certain number of deviations (about 3, often around 35 points) then running it up doesn't matter, and it plays a small role before that too. And strength of schedule makes little difference too it turns out. So with the complex rating most of your complaints are accounted for.

    Second, it's hard to measure luck just by the way balls bounce. It doesn't really matter if it makes no difference on the final score. A simpler way to look at it would be to look at really close games. A team should go roughly .500 in super close games, but the Hawks were 4-1 in games decided by 3 or less. That's 1.5 of their 2 extra wins right there. Northwestern for comparison went 3-2.

  3. We should just let Vandy start against NU this year. If they injure him it won't matter. Also we could try to convince them that Paki is our star running back.

  4. Indiana, Michigan State, Northern Iowa..... You don't need no stinking formula to know the Hawkeyes were lucky last year..... or have you developed a mathematical formula for measuring "heartbeat"? BK Link