By: Edward Egros

Apr 2016

Playoff Unpredictability

Pasted GraphicUntil recently, the Los Angeles Lakers were one of the fixtures of the NBA Playoffs, and in many seasons, the Finals. They have put together dynasties in different generations of the sport, from Magic Johnson's teams to the Shaq and Kobe era. When the Lakers were not winning titles, chances are another team was enjoying its own dynasty, like the Boston Celtics, Chicago Bulls or San Antonio Spurs. Dynasties are so commonplace in the NBA, 15 franchises in the sport's history do not have a championship (and seven of those still in existence never even made it to the Finals).

The NBA is unique in this regard: championships are won in bulk. Other leagues offer more parity, where there is a larger pool of contenders vying for a title. There may be dynasties in other sports, but there seems to be fewer of them, each shorter in duration and there stood a better chance someone unexpected can claim the sport's top prize.

Which of the four top professional sports leagues (NFL, NBA, MLB and NHL) offers the most playoff unpredictability? Is the NBA truly the most predictable? Is it significantly more predictable or marginally so?

One approach to answering these questions is by using a statistical model for each sport. Here, we will use
logistic regressions, where we will look at only wins (or points in hockey) and see how well it predicts whether a team won a championship that year. Here are some other notes for setting up this project:

- All data used begins with the 1989-90 season because
the NFL had the biggest chance to its playoff format at the turn of the new decade.

- Any season in any sport where a lockout shortened the number of games played considerably was removed (e.g., the 1998-99 NBA season, the 2012-13 NHL season, etc.)

- Though the NHL played 80 and 84 games in a few of these seasons, these numbers are not significantly different from the 82 played the rest of the dataset, so they are still used.

At first glance, every variable representing wins is statistically significant with 99% confidence, which should be obvious because you need so many wins just to make the playoffs. What matters is how well wins alone predicts championships. In statistical parlance, we will use a goodness-of-fit measure called
AIC (Akaike Information Criterion) to answer this question. As this number gets smaller, the model has a better fit. The following shows how well each model performs:

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The larger the bar, the more unpredictable the league is. Again, as expected, the NBA is the most predictable, and by a considerable margin. This model also suggests Major League Baseball is the most unpredictable, with the NFL as a close second and the NHL as a close third.

There are a number of other variables that could be added to these models to help determine who will win a championship, but the simplicity of these models makes for an easier comparison across sports.

Predicting the Masters

IMG_3374Jordan Spieth is and should be one of the favorites to win the Masters. He's had two starts at Augusta National, finished tied for second in 2014 and won it in 2015. He also has a PGA Tour victory in 2016, the Hyundai Tournament of Champions.

But, the PGA Tour's website is predicting someone different. Using an analytic formula, the site says
Phil Mickelson will win the green jacket. There are three variables used: the overall rankings for driving distance, putting and scrambling. Mickelson has the best ranking when combining all three variables, and by a lot. The second-place golfer, Jason Day, is 38 "points" lower than Mickelson but only ten points better than third and fourth place (Marc Leishman and Rickie Fowler, respectively). If this formula is completely accurate, Spieth will finish 7th.

Though the simplicity of the formula can be appreciated, any Masters prediction should include past performances. This variable is highly predictive. It explains why Fred Couples finished in the Top 20 in five of the last six years, even though he has played on the Champions Tour since 2010. It might also explain why the Masters remains the only major championship Rory McIlroy has yet to win (he has finished 8th or better the last two times at Augusta National).

Even when adding this variable, it does not take away from the argument for Mickelson. After all, he has won a pair of green jackets and finished tied 2nd in 2015, four strokes behind Spieth. It is also worth noting, of the 48 different golfers who have won the Masters, 17 won it multiple times (35.4%). Look for Mickelson, Spieth or Adam Scott to finish atop Sunday's leaderboard.