No Practice Stroke, Keep Your Head Down, Make More Putts

It was August of 2012 and I was at Enger Park Golf Course in Duluth, MN. For most of the day I had struggled with the flat stick. I knew that I needed to make an adjustment. I had heard a golf commentator note that Rory McIlroy doesn’t take a practice stroke when putting and that this frees him up to just hit the ball without thinking too much. I also realized that I had strayed from one of my regular putting keys. Namely, keeping my head down until well after the golf ball has left the blade. This helps keep your putting stroke on line. I had taken this putting tip from Gary Player a few years before. With only a few holes left to go at Enger, I decided to implement both. Right away I holed a solid putt of about 12 feet and I haven’t looked back.

Over the last few years it definitely seems like I have putted better. However, as a statistician, I find that it is necessary to see if this is really the case by looking at the numbers. So it is good that I keep detailed records with regards to my golf game. I started keeping track of putts per round in 2010. From the beginning of 2010 through that round at Enger in 2012 I played 63 rounds of golf and had an average of 33.9 putts per round. Since I implemented the aforementioned putting adjustments, I have played 71 rounds of golf and have an average of 31.5 putts per round over that span. On the surface, it looks like the putting adjustments have paid dividends as my average putts per round has decreased by 2.4 after implementing the adjustments. Once again, as a statistician, I find it necessary to dive deeper and make sure that this improvement in putting average is not due to random chance but is indeed statistically significant.

So, let’s consider the following pair of hypotheses: (1) Null Hypothesis: The putting adjustment did not improve my putting, and (2) Alternative Hypothesis: The putting adjustment did improve my putting. By the Central Limit Theorem, average putts per round approximately follows a normal distribution. This is important because it allows us to determine the probability of observing an average of 31.5 putts per round or lower given that the status quo for me was 33.9 putts per round. The probability of observing an average of 31.5 putts per round or less is the same as the probability that a standard normal random variable is less than -6.74, which is the number we obtain after standardizing 31.5 by subtracting the mean under the null hypothesis of 33.9 and dividing by the standard deviation. (Note: sample standard deviation was used in the calculation which usually means that a t-distribution should be used. However, the sample size of 71 is large enough to justify using a normal distribution.) Those familiar with statistics will recognize that the probability of a standard normal random variable being less than or equal to -6.74 is essentially 0. It follows that the probability of observing an average of 31.5 putts per round under the null hypothesis is essentially 0. Therefore we can reject the null hypothesis and conclude that the adjustments did lead to a statistically significant improvement in my putting.

In conclusion, putts per round is probably not the best stat to measure putting prowess. In fact, the PGA Tour uses the stat strokes-gained-putting as its main way to measure who the best putters are. This is because a good ball striker could have more putts per round when compared with a less skilled ball striker just because he hits more greens in regulation and as a result is usually putting from farther away than someone that misses greens and chips on. Putts per round also depends on green size. If you play a course that has small greens you will most likely have less putts per round than someone that plays a course with larger greens for the same reasons that prevail in the good and bad ball striker argument. Based off the available data though, it appears that, if you want to improve your putting, give up the practice strokes and keep your head down until well after the ball has been struck. (I must admit that the latter can be difficult as I have even strayed from it at times over the last couple of years.)