As I have already mentioned in my last post and in many others, I am interested in testing the assumptions with which we carry out our daily work. One of the assumptions that we work on, is that timeouts are useful. To test this assumption, I participated (with reader Ben Raymond, who did the actual statistics parts, i.e. the ‘work’) in a study of timeouts in the Polish and Italian men’s leagues from the last season. For the 2015/2016 Polish Plus Liga, we were able to obtain data for over 70% of the matches (143/181). We found out some interesting things.
As an explanatory note, in this post I am trying to summarise and simplify the findings and not add too much in the way of tables and figures that impact the flow of the post. Therefore there are a couple of footnotes with extra information. All use of the world ‘significant’ is in its statistical sense. The final paper with all notes, discussion, tables and figures will be linked later.
One assumption, or conventional wisdom, that I have written about is that there are more service errors after timeouts. We did not find that to be true. In fact, the opposite is true. The first serve of the set and serves after both tactical and technical timeouts produce lower error rates than serves in general play. This result could be explained in two ways. Either the conventional wisdom that is confirmed by years and years of confirmation bias is not actually true. Or professional players, instructed by their coaches, or through years of training, approach serving at these moments differently which leads to different outcomes.
|Serve category||Serves||Errors||Error Rate|
|First of set||543||62||0.114|
|Followed technical timeout||1016||126||0.124|
To test whether in fact players did approach serving differently at different match junctures, we looked also at ace percentage and perfect pass percentage. We found that the ace percentage at the start of the set was a little bit higher, and after a timeout a little bit lower, but neither of these results are significant. As far as reception quality (as measured by perfect pass percentage) goes, reception in general is worse than after timeouts. This result is not very significant.
Overall, I think we can reasonably infer, due to the lower error rate and higher reception quality, that players approach serving differently after timeouts. So maybe the conventional wisdom was once true even if it no longer is.*
The biggest theory we wanted to test is that timeouts effect sideout percentage. Here we found a very interesting thing. The sideout percentage is a remarkably robust figure. Two thirds of all serve attempts are won by the receiving team. This figure is almost exactly the same in general play, on the first ball of the set, after a tactical timeout and after a technical timeout.
|Serve category||Opp Serves||Sideouts||Sideout Rate|
|First of set||543||369||0.68|
|Followed technical timeout||1016||680||0.669|
We looked deeper to see if timeouts may actually be more or less effective in different parts of the set, and saw that there might be some small positive effect on sideout percentage by a timeout taken before the score is 10. However, overall there is no significant effect of a timeout taken at any point in the set. The same goes for score differential.
Service Series / Runs
The final area that we considered in the project was how these parameters changed during a service series. We found that the likelihood of service errors does not significantly change during a series**. On the other hand, sideout percentage does change, for the worse. After the third serve in a series, sideout percentage decreases significantly. Even though this is the one situation in which we found variation in sideout percentage, there was still no significant effect in taking a timeout.
There is no evidence, in this league, in this season, that timeouts effect the game in any useful way.
The full study can be found here.
* We also looked at Earned Sideout (Sideouts won not including serve errors) and First Ball Sideout (sideouts won on the first attack after reception). Both of these were also higher after timeouts, which is also what you would expect if serving was weaker at those times.
**It has been suggested that the third serve of a series is most likely to be an error. This conventional wisdom did not hold up.