Wednesday, February 6, 2013

Does the SEC's oversigning make a difference? Part 2

In an earlier post I showed that there is a statistically significant difference in the average number of recruits signed by SEC teams and the average number of recruits signed by the Big12, the conference with the next highest average number of signees, and by extension, all other FBS conferences.

Answering the question of whether those extra signees translates into success on the field is an entirely different question.  And it's a question that may have to wait one more post.  This post will focus on who the recruits that make up those extra signees are.

Digging into the data, I was able to uncover one piece of information that may be important in answering this question...or at the very least helps understand this advantage/perceived advantage more fully.

This chart shows the coefficients of correlation between 4-year averages of Top-100s, 5-, 4-, and 3- Star recruits, and the average recruiting ranking.  An negative number implies that as one goes up, the other goes down.  As the numbers expand outward from 0 towards 1 and -1 they indicate a stronger correlation between the two statistics.

Note:  I'm only looking at teams who finished in the AP Top 25.  Doing this is an attempt to reduce the signal to noise ratio...which is very high in this case.

Normally, I would not key in on a coefficient of correlation (CC) of .25 as anything noteworthy.  But for this particular analysis, that number may indicate something worth examining.

I say that because when I look at the other CCs, I see that there is a very weak negative correlation between average numbers of signees and Top-100 and average number of 5-Star players.  There is a weak positive correlation between average number of 4-star players.  

And then, with a CC of .25...virtually towering over its neighbors, is the average number of 3-star players.

But what does it mean?  To me, this may be evidence of who those extra signees are.  The SEC doesn't appear to be adding addtional 5- and 4- stars with their oversigning, but may be signing more than their 'fair share' of 3-stars.

This next chart breaks the relationship between the 4-year average number of signees and the 4-year average number of 3-stars into the SEC, B12, and the rest of the NCAA (not including SEC or B12).

Other than the clear advantage illustrated by the SEC's higher trendline, meaning an greater average number of 3-stars for the same number of signees, the slope of the SEC line (shown in the purple equation box on the lower right) is steeper.  The implication of this is that as the average number of signees increases, the average number of 3-stars in the SEC increases more quickly than for the rest of the NCAA, and slightly more than the average number of 3-stars in the B12.
 In other posts I've illustrated the dominance of the SEC in terms of numbers.  Considering this, and the SEC's greater number of 3-stars per number of signees, the implication is that oversigning by the SEC further reduces the number of 3-stars available to the rest of the NCAA...teams that find their core talent mostly in 3-star players.

To me, it's hard to believe that this is good for the college football world.  It's probably a good thing for SEC fans, but the trend indicates that unless oversigning is abolished, which would free up a significant number of 3-stars for other teams, the SEC's domination will remain largely unchanged.

You can download the data for this analysis from my public dropbox.

1 comment:

  1. Are those slopes really that different? Did you test an interaction term? They don't appear to be. I think the bigger issue is the mean difference in total class size.