Wednesday, December 9, 2015

Working Overtime

Overtime is one of the interesting quirks of basketball.  In some sports -- particularly low-scoring sports like soccer and hockey -- a game may end in a tie.  But in college basketball teams play additional periods -- as many as needed -- until a winner is determined.

Overtime games skew team statistics.  ESPN and other sites typically have pages of statistics such as "Points Per Game".  But if one game is 40 minutes long and another is 226 minutes long, it's not really an apples-to-apples comparison.  This is one reason analysts are fond of "per possession" statistics -- not only does it correct for pace of play, but it also corrects for overtime games.

Clearly the statistics you feed into a predictor need to be corrected somehow for overtime games.  But there's another interesting overtime issue to consider:  What's the final score of an overtime game?

One choice is to use the score at the end of the overtime(s).  The other is to treat the game as a tie.  There are intuitive arguments in favor of both choices.  The fact that Syracuse beat Connecticut suggests that Syracuse is a better team, regardless of how many minutes that took, so we should treat the game as a win for Syracuse.  On the other hand, the teams were deadlocked for six overtimes, which suggests that they're about as equal as it is possible to be, regardless of whether one team or the other managed to win the game in the wee hours of the morning.

Or maybe the game should be treated as a tie for some statistics and not for others.

As longtime readers of this blog are aware, I'm a believer in doing whatever works best.  So in this case, I made two runs of my predictor, once treating overtime games as ties and once using the actual  final scores.   In my case, the predictor performed better treating overtime games as ties.

Another possibility is to treat the final score of an overtime game as 1 or -1 (or 0.1 and -0.1 if your predictor can handle that), depending upon which team wins the overtime period(s).  This retains the won/loss information, but otherwise treats the game as (nearly) a tie.

For those of you who also have predictors, I encourage you to try the same experiment and report back which choice (if either) works better for you.