Analyzing “Luck” in College Basketball: Part II
Two months ago, I used Ken Pomeroy’s luck statistic to analyze the “luckiest” and “unluckiest” teams in college basketball. What Ken’s luck statistic is really looking at is close games. If you win most of your close games, you'll have a high luck statistic in the Pomeroy Ratings. Lose most of your close games, and your luck statistic will be low.
I looked at the winning percentages in close games of the 20 luckiest teams, 20 unluckiest teams, and 20 teams right in the middle. Sure enough the lucky group won most of their close games, the unlucky group lost most, and the middle group won just about half.
But now that two months have passed, I want to take those same teams and see how they’ve done in close games since. If winning (or losing) close games is really a skill, then the lucky and unlucky groups should continue to win and lose close games (and we'll change their names to "clutch" and "chokers"). But if close games truly are luck, then we would expect all three groups to have winning percentages close to .500.
For the same 60 teams used in the previous analysis, I noted their record in games decided by 6 points (2 possessions) or less, or games that went into overtime (regardless of the final score, since at the end of regulation it was obviously a close game). I also split out games decided by 3 points (1 possession) or less. Again, all overtime games were included in the 1 possession group regardless of the final score. You can get the data I used here.
Now we can compare each group’s winning percentage before January 19th (the date of my first analysis) and after January 19th.
Look how much the winning percentages have changed. After winning 80% of their close games before January 19, our lucky group has barely won half since. And it appears that our unlucky group has stopped choking away close games, as their winning percentage went from the teens to the forties!
Although one might still argue that in games decided by 2 possessions or less, the lucky group still has a big advantage (.5348 versus .4273) over the unlucky group. A 2-sample t test can tell us if this difference is significant.
The p-value of .213 is greater than 0.05, so we cannot conclude that the difference in winning percentage in close games between the two groups is significant. So overall we can conclude there just isn't any skill in winning or losing close games. We can further show this by plotting each teams winning percentage on a dotplot.
There is no discernible pattern between the groups. Since January 19, each group has teams that have lost a lot of close games, won a lot of close games, and everything in between.
Applying These Findings to March Madness
This shows that you shouldn’t overreact to the outcome of a close game in college basketball (and the same is probably true in most other sports too). Once you get down to the final minute, the whether you win or lose has more to do with the bounce of the ball than your actual skill level. So regardless of the outcome, if you went into Cameron Indoor and played a tight game against Duke, you played very well. And if you played a close game at home against Prairie View A&M, you shouldn’t be happy with your performance.
Looking ahead to March Madness, two highly rated teams are currently in the top 20 of Ken Pomeroy’s luck statistic. They are Villanova and San Diego St. Combined, those two teams are 15-2 in games decided by 2 possessions or less or overtime games. Both teams could be as high as a 2 seed. Considering that we know neither of those teams “knows how to win in the clutch,” they’re both probably being rated too high. It’s not that either team is bad; it’s just that if they had a record closer to .500 in their close games, they’d have a few more losses and would drop a few seed lines.
The typical comeback to that is “But they did win those games!” Yes, they did, and I agree that they should be seeded higher since they did win those games.
But we’ve shown here that their higher seed is not due to any additional skill either team possesses. It’s merely due to the fact that they got lucky in their close games. And in March, that luck can run out at the most inopportune time, as Seton Hall just showed Villanova in the Big East tournament.