NFL Referees 2009 and Teams' Performance Compared To Expectations

This piece looks at which referee crews in 2009 had a strong correlation between game results and what people expected for the game.

In a perfectly predictable crew, all things being equal, the home team's margin of victory or defeat would correlate almost perfectly with the betting line that for the most part tends to give an indication of the expected result for the game. (Of course, people who set the betting line are not solely focused on the expected result -- they are also focused on what betters' expectations of the results are, but we put that minor flaw to the side in this analysis because it is difficult to account for.)

Also for a perfectly predictable crew, all things being equal, the home team should win more often when it is heavily favored by the betting line and it should lose when it is the heavy underdog according to the betting line.

Is it good to be a perfectly predictable crew? Perhaps yes -- maybe being perfectly predictable means that the crew makes calls in the way that both teams expect, so they perform up to (or down to) their abilities. Meanwhile, a crew that has unpredictable results might reflect that they have unexpected interpretations of the rules and good teams cannot perform up to their expectations.

Let's take a look at two yardsticks -- correlation of the betting line to whether the home team won and correlation of the betting line to the home team's margin of victory (or loss).

Here are the rankings. The most predictable for 2009 is listed first:
1. Bill Leavy
2. John Parry
3. Don Carey
4. Jeff Triplette
5. Walt Coleman
...
13. Carl Cheffers
14. Ron Winter
15. Alberto Riveron
16. Pete Morelli
17. Scott Green

The Super Bowl referee for the Saints-Colts game is Scott Green, who had the least predictable game results in the regular season as correlated to the betting line. (Keep in mind the Super Bowl has an all-star crew so it is not Scott's usual crew.)

How did Scott Green rack up the least predictable results in the regular season? Let's take a look at some of the results compared to the betting line in his games.

You'd think that games where the home team is heavily favored, they would most likely win the game and vice-versa. But Denver as a home team was heavily favored (9.5 points) over Kansas City in week 17 but lost by 20 points. The Giants as a home team were heavily favored (9 points) over the Panthers in week 16 and lost by 32 points. Meanwhile, the Redskins as a visiting team were pretty favored (6.5 points) over the Lions in week 3 but lost by 5 points.

Other minor upsets were the Chargers as a home team was favored (3.5 points) over the Broncos in week 6 but lost by 11 points. The Steelers as a visiting team was favored (3 points) over the Bears in week 2 but lost by 3 points.

It turns out that the betting line did not help you predict which team would win the game. The upsets were randomly distributed along the betting line in his games.

For other referees, the home team won in the games where it was the most favored and its losses were clumped toward where it was the least favored. So the results correlated strongly to the pre-game betting line.

The specifics are that Scott Green had an -0.076 correlation between the betting line and the home team's margin of victory (17th out of 17 crews) and an 0.198 correlation between the betting line and whether the home team won (15th out of 17 crews).

If this holds up for the Super Bowl, then it suggests that the result of the game will not correlate well to the betting line. Perhaps teams do not perform in line with their expectations in Scott's games as much as they do in games with other crews...