## Golf Stat Blog

### Correlation and Causality: where are your real areas for improvement

Ask any statistician and they will tell you that the biggest hurdle in data analysis is confusing correlation and causality. Getting these two ideas mixed up can cause you to focus on the wrong thing waisting time and not yield any improvement. Let's get our definitions in order first.

Correlation - a mutual relationship of stats - that is that they vary together.

Causality - the outcome of one stat directly effects the second stat - that is the first causes the variance in the second.

Let's get a little less abstract and look at a few stats to put this into perspective - Score to Par and GIR Percent. These two stats tend to move together, which makes sense - the idea being that if you have a high GIR Percent your Score to Par should be pretty good as well. The opposite is also true if you have a low GIR Percent your Score to Par will tend to be higher. There is a correlation between these two stats, but is there a causal relationship? While it may be true that a players Score to Par may be changed because of their GIR performance, it isn't always the case. Good up and down performance can overcome missing a green in regulation and still make par. By only looking at Score to Par and GIR Percent it could be assumed that to improve Score to Par a player should work on their GIR shots, but that may not be the whole story.

The first place I would check is the Performance DNA (or strokes gained if your stat program has it) to see where the most stokes are being gained. It may turn out to be that the players driving performance is the real issue, causing both the GIR Percent and Score to Par to be less than desirable. If that is true it would show that the driving performance has a causal relationship (causality) with GIR Percent and Score to Par, and that GIR Percent and Score to Par are correlated.

When looking to improve skills, it's important to look deep enough to see what is causing the performance gaps and what is correlated. This means looking into the stats enough the see the whole picture and trying to use the numbers to support different possible scenarios to see which is most likely. Always look for the cause instead of assuming it - one stat may turn out to be correlated and not causal.

### What the movie The Legend of Bagger Vance taught me about golf statistics

If you haven't seen the movie "The Legend of Bagger Vance" you should - it was a good movie, but it also had one line that provides a lesson about golf statistics that should be considered. First lets get those who haven't seen the movie caught up.

The basic storyline in the movie is about Randolph Junuh, a golfer from Savanna Georgia who was convinced to play in an exhibition match against two of the worlds greatest golfers in an attempt to save a newly built golf resort, and to some extent all of Savanna, during the great depression. Junnuh (played by Matt Damon) was from Savanna and showed incredible potential as a young player before he was drafted and sent to war. When he returned his experience in the war caused such internal strife that he could no longer play golf as he once did, but with the town of Savanna depending on him so much he decided to play. At this point a mythical caddie named Bagger Vance (played by Will Smith) appears and helps Junnuh to find his "authentic swing" by quieting his inner demons allowing him to finish the exhibition match one stroke behind the other two due to a penalty he called on himself. It was a good movie, but the lesson to be learned can be found when the narrator described the three players in the match.

The three players in the exhibition match were Junnuh, the main character from Savanna, Bobby Jones (played by Joel Gretsch) and Walter Hagen (played by Bruce McGill). At the opening hole in the exhibition the narrator says:

"Hard to imagine three more different approaches to the game of golf.
Bobby Jones' swing was a study of grace in motion.
He had a way of making the difficult shots look easy and the easy shots look even easier.
Hagen, on the other hand hit more bad shots in a single game than most golfers do in a season.
But Hagen had long ago learned one thing: Three lousy shots and one brilliant shot can still make par.
And Junuh? Well, even now I can't think of it without wincing."

"Three lousy shots and one brilliant shot can still make par" - it may not be the best strategy, but it is true. Every golfer has different strengths and weaknesses in their game, and tracking performance with a golf statistics tool can help make those clear. The fastest way to achieve better performance is to strengthen the weak parts of your game but sometimes you can hit a wall.

Watch out for the point of diminishing returns, that is, watch for the point at which working on a particular weakness stops producing improvement. Golf statisic and diagnostic tools like Golf Stat Lab are good at showing a player their weaknesses and suggest where to spend practice time, but they also show you where you are improving and where you are not. If you have identified a weakness in your game and work on it you should see those stats improve over time. If you see that your improvement stops in those skill areas you need to ask yourself if perhaps your training methods need to be changed, or do you need to move on and work on something else?

The good thing about having strengths is that sometimes they can compensate for a weakness. Don't ignore your strengths in practice because if you can make them your brilliant shots then you can sometimes cover for your lousy shots with them.

If you see that you can gain the most strokes on putting, then work on putting. If you continually work on putting and get a little better but then find that you can't seem to reach the next level of performance with your putts, then consider switching to work on your greenside shots. If you can make your greenside shots better to leave the ball closer to the hole, then your putting will be easier. Putting may still be a weakness, but because you have minimized its impact on total scoring with brilliant greenside performance you can still score better. You can go back and work on putting later but in this scenario working on your greenside shots was the better use of time.

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