I was looking over the year-end stats for pass offense and defense earlier today, just to see where the Falcons sort of rank in certain areas.
I was focusing mainly on completion percentage, yards per attempt, 1st downs per attempt, big (20+ yd) plays per attempt, sack rate, and quarterback rating.
Atlanta grades well in 5 of those 6 categories, ranking in the Top 7. They led the league in completion % and 1st down rate. The lone category where they performed poorly was big plays, where they were 29th in the league.
Defensively, the Falcons fared much worse, ranking average or below average in all but 1 category. They were 16th in completion% and 1st down rate, 21st in YPA and big plays, 27th in sack rate. But they were 5th in opponent passer rating.
And after looking over the numbers, I started thinking about whether these numbers really mean anything. So I wanted to see how they correlated with wins. So I calculated the correlation coefficient
for each. And just for the sake of comparison, I also calculated it for these 6 categories as well as points scored/allowed, passing yards, touchdowns, and interceptions.
I'm sure it wouldn't take most people more than 1 guess what correlated the most with wins, it was points scored. It had a coefficient of 0.792. The closer you are to 1.0, the higher/closer the correlation, the closer you are to 0, the lower the correlation. But what I thought was interesting was that QB rating came in second at 0.730. Also interesting was that 1st down rate was at 0.706.
Interceptions had a negative correlation of -0.652, which means that as you throw more interceptions, the less likely you are going to win.
After that, it proceeded as such:
Completion Percentage: 0.628
Yards Per Attempt: 0.625
Big Plays/Attempt: 0.342
Sack Rate: -0.170
Now that's all for offense. I did the same for defense. And while the correlations did follow the same basic order, they were much less stronger.
Points Allowed: -0.736
Passer Rating: -0.539
Yards Per Attempt: -0.382
Sack Rate: 0.375
1st down Rate: -0.324
Completion Pct: -0.251
Big Plays/Attempt: -0.182
- Obviously, this is by no means a comprehensive study, and sweeping conclusions would require at least 10, if not 20 or more years of date. And obviously, it'd be interesting to factor in postseason success and whether that changes things. And of course the fact that this is only measuring passing still leaves about 40% of the game unaccounted for.
- But it is interesting that passing yards is still used as a measure of quality of a defense, yet it has the flimsiest correlation to wins, at least this year it did. Looking at yards allowed, it's practically zero, basically meaning that it has almost no relation to winning football games.
- It's interesting that getting 1st downs on offense throwing the ball has a fairly high correlation, but giving them up on defense doesn't have that much of a correlation.
- Interesting to see how sack rate on defense correlates better with winning (and more so than several other categories), but correlates very poorly on offense in terms of sacks allowed.
- Also seems to suggest that Cold Hard Football Facts way of looking at team's offensive/defensive passer ratings as their main tool of measurement is not as iffy as I originally thought. Outside points scored, their probably isn't a better way to really judge the good teams from the bad ones.
- Also that the positive correlation between scoring points and winning is stronger than the negative correlation of allowing points and winning. But obviously, it's not a huge discrepancy. But if you had to choose between having an elite scoring offense, or an elite shutdown defense, you would probably win more (regular season) games.