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Analyzing “Luck” in College Basketball: Part II

Luck and basketballTwo 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.

The Analysis

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.

Tabulated Statistics

Tabulated Statistics

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.

2-sample t test

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.

Dotplot

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.

Buyer beware.

Comments

Name: Mark Johnson • Tuesday, March 18, 2014

I enjoyed the article. I do believe though that certain people have the ability to "will" a win. The person that comes to my mind is Magic Johnson. He called the end of the game "winning time". I would be interested to know if the Los Angeles Lakers had the "luck" factor through their many championships during the Magic Johnson era. If I were a betting man, I would say yes.


Name: Kevin Rudy • Wednesday, April 9, 2014

I collected every playoff game that Magic Johnson played in. Out of the 186 games, only 31 were decided by one possession. That's not very many close games! And of those 31, the Lakers won 17 (55%), so that is pretty close to what you would expect.

When you take 2 possession games (there were 62 of them), their winning percentage increases slightly to .629. But that's still pretty far off from the .804 winning percentage the "lucky" group displayed in the college basketball analysis.

I think the biggest takeaway from the numbers I looked at is actually the blowouts. Of the 127 playoff games Magic Johnson won, 71 (56%) were won by 10 points or more and the average margin of victory in those 71 games was 18 points!

So these numbers suggest that Showtime Lakers weren't really winning championships by constantly "coming up clutch" in close games. They were winning by blowing teams out.


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