Wednesday, January 30, 2013

Ranking every possible super bowl matchup (and then some)

For those of you paying attention to sports in any way whatsoever you may have noticed that the super bowl is coming up this weekend.  It's pretty easy to find a wide array of articles and analysis about it, and a week or two ago I came across an article at the bleacher report with the title:

Ranking Every Possible Super Bowl Matchup
(http://bleacherreport.com/articles/1483126-power-ranking-every-possible-super-bowl-matchup?hpt=hp_t3 )

I was excited by the title because I thought this was going to be a ranking of *EVERY* super bowl matchup between every team to figure out which team would actually be the strongest, and not just a simple rundown of what the situation was from this point onward.

Since that was a disappointment, I figured I'd just do it myself.  Right?

Well, it's easy enough (if not a touch tedious) to pull down the scores from every game of this season.  Luckily, the NFL plays a relatively small number of games so it's a fairly reasonable set of data.  At most a team will play another team twice, so we can produce a somewhat odd 32x64 partially filled matrix containing all the win information in one direction and the loss information in the other direction.

The important thing that this allows us to do is to calculate some means and standard deviations.  Specifically, we can check out the mean score of each team both from an offensive and defensive standpoint.  The offensive score is the score that team was able to produce, and a higher score should indicate a better offense.  The defensive score is the score that the team allowed the other team to produce, and a lower score should indicate a better defense.

Right off the start this gives us some good numbers to check out - what teams performed the best and worst throughout the season as well as how consistent given teams were.

The Patriots showed the best offense this year, coming in just over 34 points a game on average.   

The worst team?  Sorry, Kansas City Chiefs fans.  Do I have any readers who are Kansas City Chiefs fans?  Sorry, your offense only produced a little over 13 points on average.

The best defense goes to the Seattle Seahawks, only right around 15 and a quarter points per game allowed on average, and the worst defense goes to the New Orleans Saints, allowing on average just over 28 and a quarter points per game.

If we compare the average points of every team against every other team we can get a feel for what their records would have been if a) every team played every other team once and b) every team had the same defense.  Obviously one of those is a bit larger of a jump, but let's keep an open mind for the moment.  This is how things would work out:


Team (offense) Count wins Count losses
New England Patriots  31 0
Denver Broncos  30 1
New Orleans Saints  29 2
New York Giants  28 3
Washington Redskins  27 4
Green Bay Packers  26 5
Atlanta Falcons  25 6
Houston Texans  24 7
Seattle Seahawks  23 8
Cincinnati Bengals  22 9
Baltimore Ravens  21 10
San Francisco 49ers  20 11
Tampa Bay Buccaneers  19 12
Minnesota Vikings  18 13
Dallas Cowboys  17 14
Detroit Lions  16 15
Chicago Bears  15 16
Carolina Panthers  13 17
Indianapolis Colts  13 17
San Diego Chargers  12 19
Buffalo Bills  11 20
Pittsburgh Steelers  10 21
Tennessee Titans  9 22
Cleveland Browns  8 23
St. Louis Rams  7 24
Oakland Raiders  6 25
Miami Dolphins  5 26
New York Jets  4 27
Philadelphia Eagles  3 28
Jacksonville Jaguars  2 29
Arizona Cardinals  1 30
Kansas City Chiefs  0 31

Due to the way this works out through mean comparisons, this is actually a ranking of how every team would do in a super bowl against every other team.  The Patriots would beat anyone, the Broncos would beat everyone but the Patriots, etc.  

We can find the probabilities (roughly) associated with this actually being the outcome by taking into account the stability of those means via their standard deviations.  A proxy for this that I'm calling good enough for our immediate purposes is the probability associated with t-tests between these individual means.  The product of these reversed probabilities (due to the fact that a win or loss is more probable when the p-value is small; e.g. .02 should actually be .98) gives us something we can put in a table.  YES I KNOW I'M KIND OF BUTCHERING THE POINT OF P-VALUES. 

Some of these numbers are actually reasonably finite, and we can add to the above table as such:


Team (offense) Count wins Count losses Probability of occurrence
New England Patriots  31 0 0.47089515
Denver Broncos  30 1 0.019777304
New Orleans Saints  29 2 0.000572806
New York Giants  28 3 6.88355E-09
Washington Redskins  27 4 1.22143E-07
Green Bay Packers  26 5 2.99026E-08
Atlanta Falcons  25 6 7.57896E-08
Houston Texans  24 7 8.88084E-10
Seattle Seahawks  23 8 4.09893E-11
Cincinnati Bengals  22 9 1.49184E-09
Baltimore Ravens  21 10 5.36586E-12
San Francisco 49ers  20 11 1.34842E-11
Tampa Bay Buccaneers  19 12 1.50215E-10
Minnesota Vikings  18 13 1.74783E-09
Dallas Cowboys  17 14 4.93673E-10
Detroit Lions  16 15 7.0116E-10
Chicago Bears  15 16 4.6336E-12
Carolina Panthers  13 17 0
Indianapolis Colts  13 17 0
San Diego Chargers  12 19 3.8835E-10
Buffalo Bills  11 20 3.40025E-09
Pittsburgh Steelers  10 21 6.20755E-07
Tennessee Titans  9 22 1.45213E-08
Cleveland Browns  8 23 1.73087E-06
St. Louis Rams  7 24 1.08623E-06
Oakland Raiders  6 25 2.8135E-07
Miami Dolphins  5 26 1.65687E-07
New York Jets  4 27 2.73281E-08
Philadelphia Eagles  3 28 1.04094E-06
Jacksonville Jaguars  2 29 0.000267479
Arizona Cardinals  1 30 0.000383025
Kansas City Chiefs  0 31 0.137665451


You can see that things sort of follow an upside down bell curve (let's call it a valley curve) - the most probable outcomes are those at the ends, while those in the middle have a bit more noise in them.  More of those middle games are likely to be close enough to drop the cumulative associated probabilities.

What we should keep in mind is that there are a lot of potential outcomes here.  There aren't just 31 (31-0 down to 0-31), but every possible combination of individual wins/losses that would get you to that point.  There's only one way to get 31-0 or 0-31, but there are 31 ways to go 30-1 or 1-30 (you could win or lose to any given team, and each of those has a probability associated with it).  If you'd like to kill a bit more time before you get back to work you can start working out the number of ways you can get to each potential outcome.  It also explains at least a little bit of the valley curve that we have going. 

Yes, the clever among you might have just realized that this table is excluding some potentially important information.  This probability isn't the cumulative probability of all situations that would produce a given outcome, but rather the probability associated with the most likely sequence that would produce that outcome.

For example, the Broncos going 30-1 is actually the probability of the Broncos going 30-1 while losing to the Patriots.  There's another probability that they'd go 30-1 while losing to the Giants, or the Saints, or even the Chiefs (the probability of them just losing to the Chiefs *at all* in this metric is 4.57E-07; fairly unlikely).

There's also a strange coincidence here that you might notice - the Panthers and Colts actually produced the same mean score throughout the season.  There's an interesting discussion to be had about how the way points are earned (in chunks) allows this, but it's for another day.  We'll see it happen a few more times when we get to defense.

Overall these probabilities don't really instill a lot of confidence (except for the Chiefs - sorry again Chiefs fans).  We have to keep in mind that this is simply offense, and doesn't consider how difficult any teams' defense might have been.  Now that we've seen how this works we can also produce the same table based on the idea that a) every team plays every other team once and b) every team has the same offense.

Such a situation would mean that a team's defense was the only way to stand out, and we can produce the same table based on how things would play out from there:


Team (defense) Count wins Count losses Probability of Occurrence
Seattle Seahawks  31 0 0.033645703
San Francisco 49ers  30 1 5.72087E-06
Chicago Bears  29 2 3.03016E-05
Atlanta Falcons  28 3 7.53205E-07
Houston Texans  27 4 0
Miami Dolphins  26 5 5.97182E-10
Denver Broncos  25 6 4.65242E-06
Cincinnati Bengals  24 7 1.68938E-11
Pittsburgh Steelers  23 8 5.27437E-11
New England Patriots  22 9 0
Green Bay Packers  21 10 3.75177E-13
St. Louis Rams  20 11 1.21268E-13
Baltimore Ravens  19 12 0
Arizona Cardinals  18 13 5.77952E-13
Minnesota Vikings  17 14 1.17577E-13
Cleveland Browns  16 15 5.5051E-11
Carolina Panthers  15 16 2.73832E-11
San Diego Chargers  14 17 1.6091E-12
New York Giants  13 18 0
New York Jets  12 19 1.07632E-10
Indianapolis Colts  11 20 9.97422E-12
Washington Redskins  10 21 2.72878E-09
Tampa Bay Buccaneers  9 22 6.3485E-09
Dallas Cowboys  8 23 3.63465E-07
Kansas City Chiefs  7 24 9.21125E-08
Buffalo Bills  6 25 7.97968E-11
Tennessee Titans  5 26 2.93401E-05
Philadelphia Eagles  4 27 0
Jacksonville Jaguars  3 28 0
Detroit Lions  2 29 8.82456E-09
Oakland Raiders  1 30 5.65719E-11
New Orleans Saints  0 31 1.93842E-07


The same things about the other charts apply to this one, though it also gives us a picture of how strong different teams' defense was.  Unfortunately, this is also confounded with the fact that different defenses played different offenses.  We could simply look back at offenses, but those were already confounded by the fact that different offenses played different defenses.  You can see we're in a bit of a loop here.

While we're trying to think our way out of that one we can kill some time by taking a look at the average quality of defense that different teams faced throughout the season.  We can do this by averaging - for each team - the average points allowed by their specific list of opponents.   The more points that your list of opponents allowed, the easier it is to score points against them.


Team Opponent Defense
Atlanta Falcons  24.5025641
Pittsburgh Steelers  23.89198718
Cleveland Browns  23.5650641
Tampa Bay Buccaneers  23.50737179
Cincinnati Bengals  23.5025641
Indianapolis Colts  23.46634615
San Diego Chargers  23.40865385
Philadelphia Eagles  23.07948718
Jacksonville Jaguars  23.04807692
Houston Texans  22.96634615
Kansas City Chiefs  22.93269231
Baltimore Ravens  22.91121795
Carolina Panthers  22.88717949
Miami Dolphins  22.88461538
New Orleans Saints  22.86794872
Denver Broncos  22.81730769
Washington Redskins  22.81025641
Chicago Bears  22.76217949
New York Giants  22.67083333
Green Bay Packers  22.60576923
Oakland Raiders  22.55288462
Minnesota Vikings  22.53846154
Tennessee Titans  22.49038462
Buffalo Bills  22.46153846
New England Patriots  22.19230769
New York Jets  22.17788462
Seattle Seahawks  22.07467949
San Francisco 49ers  22.06730769
Dallas Cowboys  21.94230769
Detroit Lions  21.85576923
St. Louis Rams  21.62980769
Arizona Cardinals  21.39903846


Turns out things are actually pretty close when it gets to this level.  The Falcons faced the easiest defenses, with their average opponent allowing 24 and a half points.  The Cardinals - perhaps not enough to account for their fairly weak season - faced the most difficult defenses.

We can look at the same concept in terms of how well defenses performed against their opponents' offenses:


Team Opponent Offense
Arizona Cardinals  23.18269231
Atlanta Falcons  22.5599359
Baltimore Ravens  23.43974359
Buffalo Bills  20.9375
Carolina Panthers  23.58397436
Chicago Bears  22.27403846
Cincinnati Bengals  21.35801282
Cleveland Browns  22.59358974
Dallas Cowboys  23.9974359
Denver Broncos  23.49519231
Detroit Lions  22.05769231
Green Bay Packers  22.73301282
Houston Texans  23.25
Indianapolis Colts  21.77403846
Jacksonville Jaguars  23.12019231
Kansas City Chiefs  23.48557692
Miami Dolphins  22.0625
Minnesota Vikings  22.62980769
New England Patriots  21.67307692
New Orleans Saints  23.35801282
New York Giants  23.96634615
New York Jets  22.07211538
Oakland Raiders  22.34615385
Philadelphia Eagles  23.73301282
Pittsburgh Steelers  21.9974359
San Diego Chargers  22.38461538
San Francisco 49ers  23.44455128
Seattle Seahawks  22.56730769
St. Louis Rams  23.55288462
Tampa Bay Buccaneers  22.97339744
Tennessee Titans  22.73557692
Washington Redskins  23.25224359

At this level of aggregation we again seem to be washing out all useful variance.  

Overall, I'm not sure there's really enough variance here to warrant the meaningful inclusion of it unless things are really pretty close.

Speaking of close, we should at some point probably try to figure out who is going to win the *actual* super bowl.  One last combination before we get to that.  We might be able to get a little more out of offense and defense if we look at them in combination.  We can do this by combining the win/loss records for each team to produce a table like this:


Team (overall) Wins overall Losses overall
Denver Broncos  55 7
Seattle Seahawks  54 8
Atlanta Falcons  53 9
New England Patriots  53 9
Houston Texans  51 11
San Francisco 49ers  50 12
Green Bay Packers  47 15
Cincinnati Bengals  46 16
Chicago Bears  44 18
New York Giants  41 21
Baltimore Ravens  40 22
Washington Redskins  37 25
Minnesota Vikings  35 27
Pittsburgh Steelers  33 29
Miami Dolphins  31 31
New Orleans Saints  29 33
Carolina Panthers  28 33
Tampa Bay Buccaneers  28 34
St. Louis Rams  27 35
San Diego Chargers  26 36
Dallas Cowboys  25 37
Cleveland Browns  24 38
Indianapolis Colts  24 37
Arizona Cardinals  19 43
Detroit Lions  18 44
Buffalo Bills  17 45
New York Jets  16 46
Tennessee Titans  14 48
Kansas City Chiefs  7 55
Oakland Raiders  7 55
Philadelphia Eagles  7 55
Jacksonville Jaguars  5 57
      
Looks like that helps to put a bit more spread on things, though our apparent best teams aren't the ones in the super bowl.  Not shocking, as randomness can really play havoc with things when you play so few games and leave playoffs and finals up to single elimination matches.  While I'd be a bit more excited to watch a super bowl between the Broncos and the Seahawks (or the Bears and the Jaguars), that's not what we have this year.  
  
The Ravens and 49ers - going back to the earlier table - put up the 11th and 12th best offenses on average.  They're actually pretty close on that metric - the Ravens averaged 24.875 points per game, while the 49ers averaged 24.8125 points per game.  Given that their pooled standard deviation on those means is 11.70 points there's very little reason to believe that one of these teams has a substantially (or statistically) better offense.

The 49ers scored less than a tenth of a point less than the Ravens on average, though they also faced slightly more difficult opponents.  Their opponents allowed 22.0673 points on average, while the Ravens' opponents allowed 22.9112 points on average.  While this might allow us to tip things *a little* more in favor of the 49ers I'd still be hesitant to say that anything was even close to a sure thing.  I've thought about it a while and don't know if I have any meaningful way to combine points earned and points allowed by specific opponents.  

Let's take a look at defenses - the 49ers did hold up to some of the early promise of a good defense by coming up as the 2nd best, allowing only right around 17 points on average.  The Ravens were somewhat in the middle of the pack, coming up as 13th best defense with right around 21 and a half points on average.

Remember where we got caught in a loop a while ago?  One of the problems was that we had offense and defense to worry about, though at least for this pairing it seems the offenses are pretty close.  The small point difference is also offset by the difference in opponents.

If defense is where the difference is it's hardly enough to be impressed by - the difference in defensive strength is 4 points, while the pooled standard deviation is just under 11 points.

The slight advantage held by the 49ers is also shown in that last table, as they show up as 6th overall while the Ravens come in at 11th.  Even this spread isn't huge, as it's partly due to the fact that a lot of teams are actually incredibly close in terms of mean points scored or allowed.  Forcing things into wins/losses allows for sorting, but carries a lot of error in these close match-ups that could have gone either way.  Let us keep in mind that the teams that are coming up on the top of our charts didn't have perfect seasons, but the games they lost they may have lost by very slim margins. 

All in all I was hoping that one of these teams would have meaningfully distinguished themselves on something, but it seems that these two teams in the super bowl really are pretty close - at least by the numbers.  If pushed it would seem that the 49ers have a slight edge, but what that relates to in terms of a point spread is pretty tricky.  If the 49ers are able to put up a defense that's able to stop 4.5 more points than the Ravens, and both play basically the same offense (with perhaps a slight advantage to the 49ers), then we're talking about less than a one possession spread.  Four to five points is right in that range of being just covered by a touchdown but not covered by a field goal.

If I had to make some guesses, then, the best things to work from are the scores we've seen so far - offensively 24.8125 vs 24.875 points per game, defensively 17.0625 vs 21.5 (49ers and Ravens, respectively).  Opponents of each team also gave up 22.0673 vs 22.9112 points on average, scored 23.4446 vs 23.4397 on average.

So, if team A is trying to score x points and team B is trying to hold team A to y points, the relative importance of offense vs defense would dictate the weighted average that is most accurate.  Given no reason to assume anything else I'm just going to call it an even split and take a normal average.  What that would mean is that the most likely score of this super bowl (still probably pretty unlikely) would be 23.15625 to 20.96875, 49ers.  Okay, so that score is not just unlikely, but impossible.  Silly imprecise sports. 

You might be going straight to the comments to point out that you can't earn 0.00005 points in a game of *normal* football.  More important is the fact that even the rounded score of 23-21 might not be the most common.  If we head back over to my favorite historical archive of all football scores ever ( http://www.pro-football-reference.com/boxscores/game_scores.cgi ) we can see that there have only ever been 46 games with an outcome of 23-21.  Given the amount of error we're playing with here I'm willing to take this prior information into account to some degree, especially given the fact that the *very* similar score of 23-20 is over three times as likely as 23-21.

In all, my best guess would be that the scores are pretty close, and somewhere in the low 20s both.  The 49ers seem to have a slight edge, but it's football and they only get to play one game.  Repeat this super bowl 100 times and then we can talk.


More than anything, it seems that this super bowl might actually be a close game.  I say that's always what I want, sooooooo I guess I'd better watch it.

Maybe I'll record it so I can get rid of the stupid commercials. (<- flame baiting)



 >>>>Update:
Here are the raw numbers for points scored and points allowed as requested in the comments.


Team Points scored Points allowed
Arizona Cardinals  15.625 22.3125
Atlanta Falcons  26.1875 18.6875
Baltimore Ravens  24.875 21.5
Buffalo Bills  21.5 27.1875
Carolina Panthers  22.3125 22.6875
Chicago Bears  22.5625 17.3125
Cincinnati Bengals  25.0625 20
Cleveland Browns  18.875 23
Dallas Cowboys  23.5 25.53333333
Denver Broncos  30.0625 18.0625
Detroit Lions  23.25 27.3125
Green Bay Packers  27.0625 21
Houston Texans  26 20.6875
Indianapolis Colts  22.3125 24.1875
Jacksonville Jaguars  15.9375 27.75
Kansas City Chiefs  13.1875 26.5625
Miami Dolphins  18 19.8125
Minnesota Vikings  23.6875 20.875
New England Patriots  34.8125 20.6875
New Orleans Saints  28.8125 28.375
New York Giants  27.46666667 21.5
New York Jets  17.5625 23.4375
Oakland Raiders  18.125 27.6875
Philadelphia Eagles  17.5 27.75
Pittsburgh Steelers  21 20.25
San Diego Chargers  21.875 21.875
San Francisco 49ers  24.8125 17.0625
Seattle Seahawks  25.75 15.3125
St. Louis Rams  18.6875 21.75
Tampa Bay Buccaneers  24.3125 24.625
Tennessee Titans  20.625 29.4375
Washington Redskins  27.25 24.25

2 comments:

  1. The correlation between average points scored (you've labeled it "opponent defense") and average points allowed (you've labeled it "opponent offense") is -.18, which suggests, consist with lay assumptions, that teams place their focus on offense relative to defense (and vice versa). That is, there seems to be a trade-off between effort invested in offense and defense. On the other hand, there is a positive correlation between a team's rank on offense and it's rank on defense (r = .34). Wonder why that is...I guess some information gets lost in the rank. Or perhaps it has something to do with how you calculated these ranks...

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  2. Sorry, I think that's a problem stemming from how I labeled things and a failure to explain those last two charts of opponent offense and defense. Those aren't the points scored or allowed by a given team - those numbers weren't included in the post but rather just converted to those ranks.

    Opponent offense is the average number of points scored by the teams that that team played against. Opponent defense is the average number of points allowed by the teams that team played against. It was simply meant to give an idea of if some teams played sets of teams with better or worse offenses or defenses, though it does seem that things are fairly balanced.

    In relation to the correlation between ranks, there's a similar correlation (but negative) between points scored and allowed for any given team (as would be expected). I was going to post the raw numbers here but it seems that the formatting in the comments is substantially different than the formatting in the posts, so I'll just append it on to the end of the post.

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