December 10, 2013

# Geek Speak: The Effect of 3rd Down Conversion % on Points and Wins

In previous posts we’ve learned about the Pearson Correlation Coefficient, what it means and how it can be applied to analyzing a football team’s performance.

We’ll continue down that road today by looking at the correlation between successes on third downs (both offensively and defensively) and what that means to points and wins/losses.

#### Correlation between offensive 3rd down conversion %, points and victories:

 Points Wins 0.696052 0.529742015

First, looking at the 2012 NCAA third down conversion statistics on the offensive side of the ball there is a correlation between success on third downs and points scored – a strong correlation of 0.696052, which can be seen in the chart below and the slope of the line through the data.

When we look at how third down conversions affect wins and losses we see a correlation, but not as strong as the correlation to points. Notice the slope of the line is not as great as in the picture above. Why? Because the offense has a large degree of control of how many points a team scores, but has less direct control over how many points the opponent scores thereby decreasing the correlation between wins and offensive third down conversions.

In short, the offense alone does not control wins and losses (brilliant!).

On the defensive side (graphs not included), the correlation of third down conversion percentage to points is strong, but less than on the offensive side, which is an interesting note and one that we will see again and again when analyzing correlations.

#### Correlation between defensive 3rd Down %, points and wins:

 Points Wins 0.60035 -0.44608

Notice the negative correlation to wins which makes perfect sense. The higher percentage of third down conversions a defense allows the fewer wins a team is likely to have.

None of this is rocket science and most fans are probably wondering why I took the time to research and write this post.

First, it’s what I do. Secondly, while we knew that third down conversions affect points and wins and losses, we had no idea how much. Now we know.

Finally, and this may be the key takeaway going forward, using the data above we can argue that third down conversions are more important on offense than they are on defense, both in terms of points and wins.

Not all third downs are created equal. Assuming everything else is the same, the offensive third downs are more important than defensive third downs and this is important because of the implication that revelation has on “defense winning championships”.

As we’ll see in coming posts, this isn’t the only metric that contains this nugget.