Jan 11, 2012 by Cliff DeJong
NOTE: This article was written at the start of the 2012 NASCAR season to provide a better understanding of the algorithm used in our AccuPredict - NASCAR Driver Finish Predictions tool. The basis of the formula remains as described in this article, although some tweaks to the weighting of the formulas are made by Cliff after each NASCAR season.
There are at least two practices each race weekend, except in the case of rainouts, and sometimes there are more.
The last practice is called Happy Hour.
Happy Hour sometimes is after qualifying, but more often in recent years, it is before qualifying. When before qualifying, some drivers are making mock qualifying runs and those are generally faster than practice in race trim.
So, performance in Happy Hour may not be the best comparative measure of a driver's upcoming performance.
In addition, practice speeds are sometimes measured as the fastest lap a driver has made, and sometimes as the best 10-lap average speed for those drivers that run at least 10 consecutive laps.
TV commentators often have commented about the value of the 10-lap averages. Average speeds for each practice session are also available.
Practice is not usually intended to give the driver a rehearsal at a particular track, that is to familiarize him with the track itself, but serves as a means to dial in the car's handling characteristics and to understand how to adjust the car as the track changes.
A driver who dominates in practice almost always does well in the following race.
A comprehensive database of the various practice measures does not seem to be available, so I went back over the 2011 season and put together various statistics for each race.
The correlations of finishing position to several practice measures are shown in Figure 14.
The bar labeled Happy Hour is a ranking of the fastest Happy Hour speeds, while Average HH is the average speed during Happy Hour.
The Top 10 laps in Happy Hour are shown.
Because of the mixture of race trim and qualifying trim during Happy Hour, I also looked at peak lap speeds in the practice just prior to Happy Hour. This is often the first practice, which also serves to set the qualifying order and is therefore important to the driver.
As the chart shows, the fastest laps in the next to last practice are the best measure of practice, and the correlation achieved of 42% is about the same as the other measures discussed so far in this analysis.
Qualifying is important in multiple ways to a driver.
The correlation of starting position to finish position is shown in Figure 15 for the last several seasons.
Some drivers are required to start at the end of the field because of an engine change, for example, and those drivers are treated here by how they qualified.
It is not clear why the correlation has improved with time.
Correlations for the 2011 NASCAR season are again about 40%, which is about the same as the other performance measures examined this far.
Cliff DeJong (pronounced De Young), the man behind AccuPredict, is a research scientist who has been crunching numbers his entire life. An avid NASCAR fan, Cliff was introduced to fantasy NASCAR by his brother (who beat him at just about everything).
Cliff put his Carnegie Mellon Computer Science degree and Iowa State University Mathematics degree to use creating successful methods to predict each Cup race based on NASCAR statistics.
It is an obsession that has consumed untold hours.
Cliff would love to hear your comments, questions and suggestions at moc.liamg@tciderpucca