Tuesday, January 29, 2013

Average 4-year Recruiting Rankings and WL%

To follow up on my last post about recruiting, I dug into Scout.com's historical recruiting rankings and pulled some interesting stuff out of the data.

First of all, when I do the same correlation computations that I wrote about in my previous post on all NCAA teams I find that no average or single year has a correlation coefficient of greater than .36.  This means that recruiting rankings alone are poorly correlated to season win percentage.  So, I'm abandoning my hopes of an expanded season model.

One thing you can do, without interpreting or extrapolating the data, is compute the probability, given a 4-year Scout recruiting rank average, of a team finishing with a particular season W/L percentage.

For example, for the 2005-2012 seasons, there were 56 seasons in which the Scout.com 4-year average was between 1 and 10.  11 of 56 (19.6%) resulted in a season with a WL% of > 90%.  This is reflected in the upper left corner of the probability matrix.

Figure 1

To show the most relative probability of a given season WL%, I color coded the rows with the most likely season WL% as darkest green and the least likely WL% as the darkest red.  One thing that jumps out at me is that a team is most likely to have a fairly average (between .41 and .70) WL% regardless of recruiting.  This is shown by the dominance of green in the center of the chart.  The chart does show that a very high recruiting average increases the likelihood of a very successful season and the likelihood that a very low recruiting average increases the likelihood of a low WL%

So, where did NU's recruiting averages end up?

NU's 4-year averages are shown in Figure 2:

Figure 2

Those averages, plotted on the chart in Figure 1, look like this:

Figure 3

Other than 2007, AKA "The Season That Shall Not Be Recalled", NU's recruiting and WL% has formed a fairly tight shot group.  The conclusion that I draw from this is that NU has actually slightly outperformed what the probabilities would predict; based on their average recruiting ranking.

At the risk of assuming the role of Major Obvious, if NU is going to make the jump into elite status (which I would consider a WL% of >80%), NU's recruiting has to be improved and that improvement needs to be sustained over a long period of time.  If NU's Scout.com 4-year average can move into the 1-10 group, there is 40% probability that NU's WL% will be >80%.  If it continues to average about 26 the probability of an elite season is <10%, and the probability of competing for a National Championship is close to 0.

Taking each team's actual end of season WL% and dividing it by the expected WL% for that recruiting group, I can identify teams that over/underperformed that year...at as far a their recruiting ranking would predict.

For the Big 10, sorted by over to under performing over the entire period, it looks like this:

It looks to me like NU has, as I mentioned above, slightly outperformed what would be expected of their recruiting classes.  MSU's and NWU's recent successes show up clearly as well.  Michigan's average is pulled down by it's lousy 2008 and 2009 seasons.