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Monday, August 18, 2008

Rectifying a Stupid Conclusion - Preseason Polls

Georgia is #1, but should we care?

This time of year, we often hear about preseason polls and, in response, we hear that preseason pollsters don't know much this early and so preseason polls are just entertainment. One might point out, for example, that only 10 times since the AP started preseason polling (1950) was the final #1 in the top spot before the season (17%) and, more condemning, 6 times the eventual national champion was not ranked in the AP preseason poll.

But to use these numbers to suggest that the preseason poll doesn't mean much is premature and, well, wrong. I used a simple logistic model and data from the AP Poll Archive and found that preseason rankings are more important than you might think.

First, a team in the top spot in the preseason is 29 times more likely to win the national championship than if they weren't in the top spot. To clarify, that doesn't mean that Georgia is 29 times more likely to take it all than USC, but that Georgia is 29 times more likely to win it all than the average college football team. But that shouldn't surprise anyone--of course the Dawgs have a better shot then, say, Wyoming.

But ranking matters even for those at the top. The top dog, no pun intended, is almost 5 times more likely to be #1 at the end of the season than the average ranked team, 2.6 times more likely to achieve that result than other time top 5 teams, and 1.5 times more likely than the #2 team to be on top at season's end. And for the statistically minded, those results are statistically significant.

Finally, I present the results for the most comprehensive model I have tried:

The important numbers for our purposes are the odds ratios, in red, that detail the probability of a team with a particular rank winning the national championship relative to the average unranked team. Teams that start off on top are 200 times more likely to win the national championship than teams that start off unranked, and teams that are #2 at the beginning are 133 times more likely to win it all than the unranked teams, etc.

In other words, preseason polls matter, and they matter a lot--the numbers presented here are large and significant. It's good to be #1.


Matt said...

But we would expect the #1 team to be better than the #2 team, right? We would assume the pollsters know something, however small. So the real question is, removing differences in team quality, does being ranked #1 in the preseason poll help you win the championship? I don't know how to answer that.

Scott Albrecht said...

As soon as I can get my hands on the data I'm going to look into it. I agree that polls can be "sticky" sometimes, and I also hate it when Notre Dame and Michigan (as good current examples) start out way too high or jump 27 spots because they win a big game. I can already envision some interesting analyses of poll stickiness and poll love.

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