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Strength of schedule

Posted by Doug on April 10, 2006

The NFL schedule was released last week. Like most people who are neither season ticket holders nor executives for FOX or CBS, I like the new flexible scheduling plan that will allow more interesting games to be shown on Sunday nights.

As has been noted elsewhere, the toughest schedules (based on last year's records) belong to the Giants and Bengals, whose 2006 opponents were a combined 139-117 in 2005. The Bears have the easiest slate; their opponents were 114-142 last year.

But as we all know, some teams that were bad in 2005 will be good in 2006 and vice versa. And some schedules that look easy right now will actually be tough and vice versa. The question is: to what extent, if any, do the Bears have an advantage over the Giants because of their schedules. Two games? One game? Half a game?

To investigate this, I went back to 1990 and recorded three bits of data about every team.

  1. their own record in Year N-1
  2. their preseason estimated strength of schedule. I.e. the combined Year N-1 records of the team's Year N opponents.
  3. their record in Year N

For the 2005 New York Jets, for example, I have

  1. .625 (their 2004 record was 10-6)
  2. .535 (the combined 2004 record of their 2005 opponents)
  3. .250 (their 2005 record ended up being 4-12)

I then labeled every team, based on their Year N-1 performance, as either Very Bad (less than 5 wins), Bad (5 or 6 wins), Mediocre (7 to 9 wins), Good (10 or 11 wins), or Very Good (12 or more wins). I also labeled each team's projected schedule as either Easy (combined opponents record under .500) or Hard (over .500).

Take a look at the Very Bad teams, for example. The Very Bad teams with a projected Easy schedule averaged 6.44 wins the next year. The Very Bad teams with a projected Hard schedule averaged 6.63 wins. The difference is not significant, and that's the point. Here is the complete breakdown:

Average Wins in Year N
Easy Sched Hard Sched
Very Bad in Year N-1 6.44 6.63
Bad in Year N-1 7.67 7.26
Mediocre in Year N-1 7.82 8.27
Good in Year N-1 8.94 8.57
Very Good in Year N-1 8.78 10.06
TOTAL 7.73 8.27

An eyeballing of this table indicates that the estimated schedule strength is essentially irrelevant and official statistical tests confirm that. [For example, a regression of Year N record on Year N-1 record and projected Year N schedule strength produces a not-even-close-to-significant coefficient for schedule strength.]

Note that I'm not saying that schedule strength isn't important. Some teams will have harder schedules than others in 2006 and it will make a difference. The point is that these strength-of-schedule estimates that are being thrown around right now seem to have no role at all in determining teams' 2006 records.