Have you ever been frustrated because you have good and bad days on the tennis or volleyball court, golf course, or softball field? One of the reasons for the ups and downs is regression to the mean. Don’t be fooled by it!
Here’s the way it works.
Suppose your daughter has a volleyball serving percentage of 90%. Over the course of the season her daily serving percentage will vary, but her long-term average will be 90%.
In theory this means she will serve better than 90% half the time and the other half she will serve at or below that level. She will feel like a rock star on the days she serves 98%. On the days she serves 82% she will feel throwing her volleyball shoes in the trash and taking tuba lessons.
Regression to the mean is prevalent in team sports and most coaches are confused by the randomness associated with the concept.
Consider a basketball player who is a 70% free throw shooter.
He has a hot streak and makes 9 out of 10 free throws. The coach pats him on the back and gives him more playing time.
As should be expected, the player hits a cold streak and makes 5 of the next 10 free throws. The coach notices the decline from 90% to 50%. He yells at the player, benches him, and makes him run wind sprints at the next practice as a way of “motivating” him to do better.
Eventually the player will be allowed to play again and he will make 7 of the next 10 free throws. The coach notices the improvement from 50% to 70% and immediately associates yelling at the player, benching him and making him run wind sprints as the motivation that caused the improvement.
WRONG! The coach should be benched, made to run wind sprints, and yelled at for failing to understand the randomness of regression to the mean.
Out of the last 30 free throws, the player made 21 – his season average of 70%. The player had streaks where he was above the mean, below the mean, and right on the mean.
Don’t be fooled like the basketball coach!
Suppose you are a tennis player and want to improve your serve.
1. Work with a coach or teaching professional who understands the concept of regression to the mean.
2. Develop a practice routine that includes match-like play and relevant training.
3. As you practice your serve will become more consistent, thus reducing the range of the fluctuations in your daily serving percentage.
4. Stay calm, don’t be fooled by randomness. Enjoy the days when you serve above your seasonal average and don’t sell your racquets and take-up the tuba on the days you drop below it. Accepting the daily fluctuations is one of the challenges of competitive sports that can be minimized, but not eliminated.
5. Over time, with quality instruction and a match-like practice sessions you should be able to raise your season serving average. Remember, this is a long term proposition.
For additional information about regression to the mean and other subtleties of playing and coaching sports, visit the blog, Growing the Game Together by John Kessel, Director of USAV Grassroots Volleyball, http://www.teamusa.org/USA-Volleyball/Grassroots/Grow-The-Game-Blog.