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Thread: Fun with binomial probability!!!

  1. #1
    Join Date
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    Fun with binomial probability!!!

    A legitimate question for all theorists is how well do their models predict actual outcomes relative to random chance. In the case of golf theorists, the question might be how well does their preferred swing model predict superior performance?

    To do this exercise, I had to brush up on my introductory statistics and reacquaint myself with binomial probability, but I think it was worth the effort.

    In May 2011, Kelvin used his assessment of PGA Tour player mechanics to grade the swings on tour. Since Kelvin's model mechanics are based on power hitters with control (Jamie Sadlowski, Bubba Watson and pre-2009 Tiger), I would argue that an appropriate measure of his "predictive ability" is how well his selections rank in Richie's "Driving Effectiveness" (previously called "Advanced Total Driving") as published in his 2012 Pro Golf Synopsis.

    To do this, I first looked at the 2012 Driving Effectiveness rankings of Kelvin's nine Gold Medal winners:

    Player/Rank:

    Bubba Watson - 1st
    Hunter Mahan - 3rd
    Graeme McDowell - 7th
    Keegan Bradley - 10th
    Robert Garrigus - 13th
    Dustin Johnson - 24th
    Tommy Gainey - 119th
    Gary Woodland - 123rd
    Steve Marino - not ranked


    Woodland is an interesting case because in 2011 he ranked 17th in Driving Effectiveness, in the top 10% (about 190 players qualify for ranking each year). As Richie recounts in his write-up of Woodland's 2012 year, Gary's dramatic drop in the Driving Effectiveness rankings seemed to stem from changes instigated by his new instructor, Butch Harmon. Harmon sought to lower Woodland's ball flight off the tee and had him practice trying to hit it low with a high-lofted driver. Despite seeing an increase in clubhead speed over 2011, Gary wound up hitting it shorter and missed more fairways. If Gary had maintained his 2011 distance, he would have ranked 51st in 2012.

    Regarding Gainey's mediocre ranking, Richie speculated that his Driving Effectiveness was hurt by being too aggressive off the tee, particularly on par 5s.

    As for Marino, Steve never fully recovered from knee surgery in October 2011 and only played six events in 2012, missing the cut in all but two.

    In any case, taking the results at face value, Kelvin's predictive ability was truly extraordinary. Of his nine Gold Medal selections, two ranked in the top 1.5%, four ranked in the top 5%, five ranked in the top 8%, and six ranked in the top 13% (a total of 191 players were ranked).

    If Kelvin was "just guessing", and was no better than random chance at picking elite drivers, his nine selections would have been expected to be distributed more or less equally throughout the 191 player field. However, his Gold Medal selections are bunched near the top. To put numbers around his predictive skill, I calculated the probability of achieving his results by "throwing nine darts" at the list of qualified players.

    The probability of hitting two players in the top 1.5% of Driving Effectiveness out of nine throws is just 0.007, or 7 out of a thousand.

    The probability of hitting four in the top 5% are 0.0006, or 6 out of 10,000.

    The probability of hitting 5 in the top 8% is 0.0003, or three out of 10,000.

    And the probability of hitting six in the top 13% is 0.003, or three out of a thousand.


    Sounds to me like Kelvin is on to something...



    Jeff

  2. #2
    This was probably the main thing that drew me to Kelvin’s work. When I started researching the numbers back in 2011, almost all of Kelvin’s preferred players top-tier ballstrikers, particularly off the tee. The only guy the numbers don’t jive with that I can think of is Poulter. Although I call Poulter a ‘survivor golfer.’ He does whatever is necessary to get the job done. Outside of his Short Game play, he does nothing consistently well. Some years he’ll putt poorly, but make it up with good driving and Danger Zone play. Other years, he’ll struggle with the driver, play well from the Danger Zone and make putts. However, I would lean towards saying that driving is not his forte.

    But the others, particularly somebody like Garrigus who I find to be an incredibly talented ballstriker, are spot on. Bubba is a little weird because his Average Distance to the Edge of the Fairway is pretty high. And while it doesn’t sound like he’s hitting a lot of fairways averaging 58%, that is a TON of fairways for somebody who hits it as long as he does. It would be like Hunter Mahan hitting 71% of his fairways.

    Even for Gainey, he had good ballstriking metrics from longer distance and off the tee in 2011. From listening to him on an interview after he won at the McGladreys, it seemed like he had some equipment issues. IIRC, he had 12 birdie or better opportunities from 20 feet and in in that round of 60. On Tour, I think the average is about 4-5 per round. This was after he got some different sticks from Callaway.

    For Woodland, I think he’s way too conservative off the tee. I watched him twice this year and he uses the 2-iron off the tee way too often. Although I think part of that was due to a lack of confidence in the driver. Either way, he was not playing the game the way a person of his capabilities should play it like, a power player. Instead, he was an overly conservative tee shot player. As I mention in tee shot strategies, somebody of his power and clubhead speed is more effective being more aggressive off the tee.

    Here’s a look at how the list did Zone shots off the fairway/tee box. This is important because it correlates much more strongly to Adjusted Scoring Average.

    Bubba Watson – 74th
    Hunter Mahan – 44th
    Graeme McDowell – 3rd
    Keegan Bradley – 94th
    Robert Garrigus – 5th
    Dustin Johnson – 36th
    Tommy Gainey – 51st
    Gary Woodland – 89th
    Steve Marino – not ranked

    Every single player was in the top-half on Tour on these shots. And considering how well almost all of them did from the tee box, it’s obvious that Kelvin’s preferred swing mechanics produce excellent results.

    This in part is where I find Manzella’s beliefs a bit puzzling. He would rather go with players like Snedeker and Mark Wilson, far inferior ballstrikers to this list. Even the players he likes tend to have low clubhead speeds. And while David Toms is a great ballstriker, I’ve never seen any evidence of him employing something that resembles ‘the new release.’






    3JACK

  3. #3

    Charles Warren

    A while back, 3Jack pointed out that the best driver over the past five years has been Charles Warren. And then Kelvin helpfully posted a video of his swing, which is below:

    http://www.youtube.com/watch?feature...&v=t78crpZZPHk

    Fun swing to watch! Seems to have many of Kelvin's moves but not all of them. They way Warren turns his eyes way way way past the golf ball at impact seems so reminiscent of Duval to me. I'm wondering if Kelvin has any insight into why Duval, Warren (and Annika?) do that so aggressively while the vast majority of gold and silver medalists don't?

  4. #4
    nmgolfer Guest
    Wow... now there is a stable head position. A best driver coincidence? Me thinks not. Beautiful swing. He doesn't need to lift his heel much at all to get mobility. Thanks for reposting lifter.


    Quote Originally Posted by Lifter View Post
    A while back, 3Jack pointed out that the best driver over the past five years has been Charles Warren. And then Kelvin helpfully posted a video of his swing, which is below:

    http://www.youtube.com/watch?feature...&v=t78crpZZPHk

    Fun swing to watch! Seems to have many of Kelvin's moves but not all of them. They way Warren turns his eyes way way way past the golf ball at impact seems so reminiscent of Duval to me. I'm wondering if Kelvin has any insight into why Duval, Warren (and Annika?) do that so aggressively while the vast majority of gold and silver medalists don't?

  5. #5
    Join Date
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    Quote Originally Posted by Richie3Jack View Post

    Here’s a look at how the list did Zone shots off the fairway/tee box. This is important because it correlates much more strongly to Adjusted Scoring Average.

    Bubba Watson – 74th
    Hunter Mahan – 44th
    Graeme McDowell – 3rd
    Keegan Bradley – 94th
    Robert Garrigus – 5th
    Dustin Johnson – 36th
    Tommy Gainey – 51st
    Gary Woodland – 89th
    Steve Marino – not ranked

    Every single player was in the top-half on Tour on these shots. And considering how well almost all of them did from the tee box, it’s obvious that Kelvin’s preferred swing mechanics produce excellent results.

    Let's look at the probability of hitting eight players in the top half of Zone shots off the fairway/tee box by throwing eight darts at the list of eligible players (we'll exclude Marino since he was out most of the season): That probability is 0.004, or 4 times out of a thousand tries! Kelvin rules!


    Jeff

  6. #6
    I followed Woodland around at the Fry's tournament and I strongly concur he is too conservative off the tee. He was hitting 3 wood on holes every other guy in the field was hitting driver on. Many of the holes he was hitting first and had to be a half club to a full club behind them.

    Looked to me like his swing was fine, just rarely if ever hit the driver.

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