Crunching The Numbers: Under Further Review (Part III of IV)

Mark J. Rebilas-USA TODAY Sports

The previous post discovered that some statistics don't correlate with winning - at all. This prompted the next leg of my journey, where I analyzed other statistics (a LOT of them) to find out which ones really do correlate to winning. The results may surprise you.

At the end of the Part II, the regression analysis showed some interesting correlations between statistics and winning. Namely, the yards per carry metric is apparently meaningless. With a result this surprising, the only reasonable thing to do was to perform a regression analysis on more statistics in an attempt to draw some concrete conclusions. The statistics I use for my algorithm come from Team Rankings (it's an awesome site if you're a stat junkie), so I went there. As a disclaimer, I stayed with statistics in the facets I was measuring in my algorithm (running game, passing game, turnovers, and scoring), which means I left out statistics related to special teams and penalties. While that indicates this analysis is by no means exhaustive, I did analyze seventy-three individual metrics for all thirty-two teams, so it is fairly comprehensive.

In the interests of getting to the point, the tables below will only show the statistics that had a 95% confidence level - if you recall from Part II, this means their correlation coefficient has an absolute value greater than 0.3494. At the end of the post I did include a table of every metric that I analyzed should you feel inclined to look them over and draw your own conclusions.

And if you're just joining us now, check out how I got started with Part I and an explanation of regression analysis can be found in Part II. Now, onto the numbers!

OFFENSE

To start, let's look at the offense as a unit.

OFFENSE OVERALL
Statistic Correlation
Points Scored/Game 0.7050
Fourth Quarter Scoring 0.6207
Third Quarter Scoring 0.5748
Second Quarter Scoring 0.4977
Third Down Efficiency 0.3555

Nothing too earth-shattering here. The one noticeable trend is that teams that won tended to score more in the second half than in the first half (in fact, first quarter didn't even make the cut with its confidence level). While this is interesting for sure, the "score-by-quarter" metric is one that I think has the potential to be volatile. It's something I'll be paying attention to across seasons to see whether or not this trend holds or if this was merely a coincidence. Moving on to the running game:

RUSHING OFFENSE
Statistic Correlation
Rushing First Downs/Game 0.4542
Rushing Play % 0.4243
Rushing Attempts/Game 0.4184

This has much more to ponder. Remember how the yards-per-carry statistic (which essentially measures the effectiveness of your running game) was meaningless? All of the meaningful run statistics are bulk statistics. That is, they are all measurements of how often a team runs the ball, not how well a team runs the ball. I found the first down statistic to be particularly interesting. At first I chalked it up to a false correlation - it had more to do with teams that got more first downs overall being more successful than it had to do with the running game. But when I looked at the correlation for passing first downs it was only 0.22. So the fact that they are rushing first downs seems to have more of an effect. Speaking of the passing game, which statistics mattered there?

PASSING OFFENSE
Statistic Correlation
Average Passer Rating 0.6294
Yards/Pass Attempt 0.6099
Incompletions/Game -0.5405
Yards/Completion 0.5392
Passing Play % -0.4243
Completion Percentage 0.4197
QB Sacked/Game -0.3989

There's a lot going on here. If you look over the statistics that showed up here, the passing game takes on the opposite characterization from the running game. The important metrics here for the most part measure how well the ball is thrown, not how often it's thrown. In fact, the passing play percentage metric has a negative correlation with winning, meaning that losing teams threw the ball more often. Considering this, Andy Reid's success in Philadelphia sounds miraculous given his allergy to handing the ball off. Jokes aside, part of this negative correlation might come from the idea that bad teams pass more because they're trying to dig themselves out of holes. It's hard to say for sure, especially when reviewing the other statistics up there. For example, there is a strong negative correlation with incompletions... but no corresponding strong positive connection with completions. This apparent trend that passing the ball is more about efficiency than anything else is something I'll touch up on later.

DEFENSE

Of course, football isn't just about offense. There's a reason why the phrase, "Defense wins championships" exists. Take a gander at some of the numbers for the defensive side of the ball:

DEFENSE OVERALL
Statistic Correlation
Points Allowed/Game -0.7617
Second Quarter Scoring -0.6299
Fourth Quarter Scoring -0.5320
First Quarter Scoring -0.4635
Third Quarter Scoring -0.3983

Just to reiterate, the negative sign indicates that as the values for the metrics decrease, wins increase. This makes sense for a lot of defensive stats, which is why there are more negative coefficients on this side of the ball. There is a much stronger correlation here with points than the offense had, with all four quarters being represented (although third down defense is noticeably absent). Interestingly enough the trend with score-by-quarters does not really exist here, which reinforces my suspicion that it might be a coincidence. The only possible connection I can think of would be the idea of "stomping out momentum" that the opposing offense might be generating at the end of each half. Again, the more likely explanation here is simply coincidence. Now, how do run defenses fare?

RUSHING DEFENSE
Statistic (Opponents) Correlation
Rushing Play % -0.5186
Rushing Attempts/Game -0.4693

The message here is pretty clear, and it's a tall task for any football team: don't stop the run; force your opponent to abandon it entirely. Logically speaking, if you're unable to stop the run your opponent is unlikely to quit handing the ball of, but we've previously seen how little yards per carry allowed has to do with winning. This means some of the onus falls on the offense to build a lead and force the opponent to play catch-up with the passing game... but at the same time this contradicts the established trend that teams who score later in the game win more often. So what is the bottom line here? I'm going to use this as reinforcement that the score-per-quarter trend is a coincidence since more evidence exists to support the "more running means more winning" concept. Does a similar "less passing means more winning" trend exist with the passing game?

PASSING DEFENSE
Statistic (Opponents) Correlation
Average Passer Rating -0.6205
Passing Play % 0.5215
QB Sacked/Game 0.4758
Incompletions/Game 0.4244
Yards/Pass Attempt -0.4233

THE TREND SAYS THAT THE MORE TEAMS PASS, THE MORE THEY LOSE.

The short answer is, "emphatically yes." Look at that correlation for passing play percentage. That means the more your opponent passed the ball, the more games you won. The other statistics refer back to the "passing efficiency trend" I mentioned in Part II; they're all associated with disrupting the quarterback's ability to perform. Sacks, yards per attempt, incompletions, passer rating... they all point to making sure the quarterback is ineffective. And when combined with the passing play percentage, it makes sense. If you can force poor quarterback play and then force the opponent to abandon the other dimension to their offense in relief, you get a pretty simple formula for success.

TURNOVERS

Turnovers: the magic buzz word of the NFL. It's impossible to turn on any football analysis show without some pundit mentioning the importance of turnovers. But there is a lot of data buried underneath that word. How often did your offense fumble? How often did they recover those? What's more valuable, interceptions or interception percentage? Numbers don't always have the answer, but in this case they do:

TURNOVERS
Statistic Correlation
Turnover Margin/Game 0.6560
Interceptions/Game -0.5353
Giveaways/Game -0.5289
Interception % -0.4821
Takeaways/Game 0.4541
Statistic (Opponents) Correlation
Interceptions/Game 0.4797
Interception % 0.4554

The first noticeable observation is that turnovers seem to focus on offensive performance more than defensive performance. I'm not very surprised that fumbles don't really show up here; they tend to be more random than interceptions and a lot of them are based on luck. Interceptions have their fare share of luck too, but a good coach can disguise coverages and apply pressure to induce a pick. The same really can't be said for fumbles. It's also interesting how turnover success is more dependent on a team's ability to take care of the football over its ability to take it away from their opponent. I would say this makes sense; by mitigating error a team is increasing the odds that the opponent will make more than them. It's also worth noting that other than scoring-related statistics, turnover margin had the highest correlation to winning than any other metric I analyzed.

The Verdict (Part III)

THE NFL IS NOT A PASSING LEAGUE - IT'S A QUARTERBACK'S LEAGUE.

After all of these numbers, what conclusions can we draw? To put it bluntly, the NFL is not a passing league. It is a quarterback's league. There is a distinct difference here. It's not about filling the air with footballs; if anything, the evidence suggests this is how you lose. It's about giving your quarterback an environment to succeed and then having one that can execute consistently and efficiently. Success happens when a team complements this with a healthy dose of the running game (preferably more than fifty percent). It doesn't even matter how well the running game is working - the key is to just keep handing it off. Likewise, defenses thrive by having the ability to compromise the play of the opposing quarterback and forcing an abandonment of the running game, which is a potent combination.

So now, the big question, the one I know we all care about: how did the Eagles fare in these metrics? I look at exactly that in the conclusion to this series in Part IV.

For Reference

Should you have some extra time on your hands and an interest in this topic, the chart below documents every statistic that I analyzed:

OFFENSE OVERALL
Statistic Correlation
Third Down Efficiency 0.3555
Points Scored/Game 0.7050
First Quarter Scoring 0.3248
Second Quarter Scoring 0.4977
Third Quarter Scoring 0.5748
Fourth Quarter Scoring 0.6207
DEFENSE OVERALL
Statistic Correlation
Third Down Efficiency -0.3402
Points Allowed/Game -0.7617
First Quarter Scoring -0.4635
Second Quarter Scoring -0.6299
Third Quarter Scoring -0.3983
Fourth Quarter Scoring -0.5320
RUSHING OFFENSE
Statistic Correlation
Rushing Attempts/Game 0.4184
Rushing Yards/Game 0.3028
Rushing First Downs/Game 0.4542
Yards/Rush Attempt 0.0517
Rushing Play % 0.4243
Rushing First Down % 0.2296
Rushing Yards % 0.1206
PASSING OFFENSE
Statistic Correlation
Pass Attempts/Game -0.2741
Completions/Game -0.0333
Incompletions/Game -0.5405
Completion Percentage 0.4197
Passing Yards/Game 0.2207
Yards/Pass Attempt 0.6099
Yards/Completion 0.5392
QB Sacked/Game -0.3989
QB Sacked % -0.1267
Passing First Downs/Game 0.2161
Passing First Down % -0.2194
Average Team Passer Rating 0.6294
Passing Play % -0.4243
Passing Yards % -0.1206
RUSHING DEFENSE
Statistic (Opponents) Correlation
Rushing Attempts/Game -0.4693
Rushing Yards/Game -0.2575
Rushing First Downs/Game -0.2559
Yards/Rush Attempt -0.0087
Rushing Play % -0.5186
Rushing First Down % -0.1728
Rushing Yards % -0.1236
PASSING DEFENSE
Statistic (Opponents) Correlation
Pass Attempts/Game 0.2556
Completions/Game -0.0414
Incompletions/Game 0.4244
Completion Percentage -0.3954
Passing Yards/Game -0.1365
Yards/Pass Attempt -0.4233
Yards/Completion -0.1752
QB Sacked/Game 0.4758
QB Sacked % 0.3410
Passing First Downs/Game -0.1087
Passing First Downs % 0.3055
Average Team Passer Rating -0.6205
Passing Play % 0.5215
Passing Yards % 0.1236
TURNOVERS
Statistic Correlation
Interceptions/Game -0.5353
Fumbles/Game -0.1820
Fumbles Lost/Game -0.2127
Fumbles Not Lost/Game -0.1685
Giveaways/Game -0.5289
Takeaways/Game 0.4541
Turnover Margin/Game 0.6560
Interception % -0.4821
Fumble Recovery % 0.0933
Giveaway Recovery % 0.0371
Takeaway Recovery % 0.1138
Statistic (Opponents) Correlation
Interceptions/Game 0.4797
Fumbles/Game 0.1609
Fumbles Lost/Game 0.2995
Fumbles Not Lost/Game 0.0127
Interception % 0.4554
Fumble Recovery % -0.0933
Giveaway Recovery % -0.1139
Takeaway Recovery % -0.0371
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