Tuesday, November 16, 2010

NCAA FBS Complex Invasion Sport Model - An Overview

Since the simple model of NCAA FBS production is rather limited, as I explained earlier, I wanted to create a model of NCAA Football Bowl Subdivision (FBS) productivity that goes beyond the number of points scored by the team and the number of points scored against the team; or as some in the media seem to focus on the point spread between points scored and points surrendered.

In order to do this, I am analyizing both the team's offensive production (in a later blog) and the team's defensive production (in a later blog). But for now, I want to give an overview of how I am setting up the complex invasion sport NCAA football production model, and give credit to those who have thought (and wrote) about this idea before me.

First, Bill Gerrard in 2007 wrote a paper in the International Journal of Sport Finance, where he coined the phrase "complex invasion sports" and wrote about how to set up modeling a team sport production function. Basically Gerrard tells us that the actions on the field can be attributed to the team's offense and the team's defense. From the offensive perspective the team actions either increase or decrease the offenses scoring opportunities and from the defensive perspective the teams actions allow the team's opponent to either increase or decrease their scoring opportunities. Obviously, not all scoring opportunities result in a score, so the production model needs to incorporate the rate (or efficiency) at which the scoring opportunities are converted into scores on the offensive side of the ball and the rate at which the team's opponents scoring opportunities are converted into scores on the defensive side of the ball. The offensive conversion rate relates to the teams scoring and the defensive conversion rate (i.e. the team's opponent) relates to the opponents scoring, or the team's points surrendered, which result in the final game outcome. It is with points scored and points surrendered where the simple team production model starts. Thus the simple team production model misses a lot of the actions that take place on the field and impact the final game outcome.

Second, from the book The Wages of Wins (by Berri, Schmidt and myself), we present a production model of the National Football League (NFL) that revolves around four areas in terms of the offensive and defensive productivity. Dave Berri provides a much more rigorous presentation of the NFL model in a book chapter he wrote in 2007, and it is the model from both sources that I draw heavily on in the creation of the NCAA FBS production function. Given that I am standing on the shoulders of giants, let me go through the four general factors that I model NCAA FBS productivity.

NCAA FBS production is determined by:
1. the ability of the offense to acquire the football,
2. move the football down the field,
3. maintain possession of the football, and
4. the efficiency at which teams score points.

Offenses that are relatively more productive in achieving these four factors than other NCAA FBS team offenses are deemed to be more productive and thus will be ranked higher than offenses that are not as productive. Defense is modeled in the same way, but better defenses are ones that in essence do the opposite of the offense.

Specifically, defense is also modeled by:
1. the ability of the defense to keep the football away from their opponent,
2. reducing their opponent from moving the ball toward a scoring attempt,
3. reducing their opponent from maintaining possession of the football, and
4. reducing their opponents efficiency of scoring points.

So that's an overview of the NCAA FBS Complex Invasion Sport Model. What I still need to determine are:
1. the actual on-field variables for each of the four production factors,
2. statistically determine if the variables are significant with respect to the offense scoring or the defense keeping their opponent from scoring,
3. the marginal impact (or weight) each variable has on offense/defense scoring,
4. the impact that different conferences have on offense/defense scoring, and
5. anything else I have forgotten while typing this up.

1 comment:

  1. Don't you have the #1 factors swapped between offense and defense? I.e., the defense acquires the ball, and the offense keeps it from the opponent?