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Wednesday, September 10, 2008
 
Another Statistic to Measure a Batter's Future Performance

If you are one of those people convinced that future performance at the plate can be predicted by using some creative formula and crunching a bunch of numbers, Ron Shandler of USA Today mentions a statistic that I had never heard of before, the "Expected Batting Average" (Batters Don't Always Live Up (or Down) to Expectations):
It does start with a batter's ability to distinguish between balls and strikes, which we can measure using his walk/strikeout rate. Once he's determined a hittable pitch, we can measure his contact rate: (at-bats — strikeouts) / at-bats. But once contact is made, we enter a gray area.
The odds of a batted ball falling for a hit are only partially within the batter's control. The stronger his power and speed skills — along with his propensity to hit the ball on the ground, in the air or on a line — the more control he may have over the outcome. But even the hardest-hit ball can become an out.

"Expected batting average," or xBA, calculates what a player's batting average should be based upon these component events along with a normalization for aberrant batting average on balls-in-play (BABIP) levels.
I have always been skeptical of using complex mathematical formulas to predict a batter's future performance. And it's not because I don't understand them or consciously don't want to try to understand them, which is what the statisticians like to say about the "traditional-minded" scouts. Here is my explanation. In one game the ball can look like a beach ball floating at 45 mph, and in another game the ball thrown by that same pitcher looks like a golf ball darting at 125 mph. I don't know why that is, and there is no formula or computer that can be used to explain it. It's called "being in the zone," and it's just one of those things in which the baseball gods have been toying with batters ever since the game was invented. But it definitely drives statisticians and lawyers crazy....





10 Comments:

This projections fails to recognize changes in situations. For instance, last year the batter in question had a really good batter behind them and they got good pitches. This year, the good batter behind the player in question left via free agency or a trade (a la Manny Ramirez and David Ortiz). Certainly you would have a different expectation. There are lots of other variables that change and make predictions far less reliable than the USAToday author makes it seem.

Anonymous Marvin Schuldiner -- 9/10/2008 10:32 AM  


Rick--

I’d probably have trouble hitting a beach ball floating at 45 mph, so I can’t relate directly to your analogy, but I’ve certainly noticed the same phenomenon in other sports I play. Sometimes it feels like the basketball rim is the size of a boat, other times it feels like the ball is too big to fit through the hoop. Same with golf and every other sport I play (poorly). There are good days and bad days and hot streaks and cold streaks in all sports. That said, I’m not sure I understand your argument. Are you saying that a basic statistic like batting average is no help in predicting future performance? I don’t think that’s your argument, and I would imagine you would agree that a .350 hitter in the major leagues (over a reasonable number of at bats) would have a greater chance of getting a hit his next time up as compared to a .150 hitter in the major leagues. xBA, to the extent it accounts from some of the “luck” involved in getting a hit in baseball, just seems to be an attempt to improve the basic batting average metric to serve as a better predictor of future success. It’s obviously not even close to an exact science, and there are many other variables that need to be taken into account, but I have to think these measures at least help the “traditional” methods of scouting and evaluating performance. No?

Anonymous Gabe Feldman -- 9/10/2008 3:12 PM  


Gabe,

Hitting a baseball involves a completely different psychological element than exists in other sports. Batters often tell reporters after the game, "I'm just seeing the ball well right now." Players in other sports don't make those types of statements. Basketball players don't say "the rim looks bigger right now"; golfers don't say "the ball is looking bigger right now" or "the green doesn't look as far away right now"; and football players don't say "I'm in the zone catching the ball at the moment." I played football and basketball in high school, and just didn't experience even close to the psychological aspects in trying to hit a baseball on a consistent basis. Perhaps that's why baseball players are much more superstitious than players in other sports. And perhaps that's why you see hitters do the same exact silly routines each and every at bat -- the reason is because they are trying to maintain that feel of staying in the zone. I don't expect any of this to make logical sense because it's not capable of being proven, but there is definitely something more to it than simply saying everybody has good days and bad days.

Blogger Rick Karcher -- 9/10/2008 5:17 PM  


Rick—
I am happy to agree with you that baseball involves a large psychological element, but I still don’t see how that impacts the utility of the batting average or expected batting average metrics.
I would be interested to hear what the folks over at the situationist have to say about your argument re the psychological elements of other sports compared to baseball. I think a lot of it depends on the level of play you’re talking about, but, personally, I think hitting a golf ball has to rank up there with hitting a baseball. I have seen plenty of golfers get “in the zone” and hit 10 perfect shots in a row, only to flub the eleventh shot and then proceed to hit 10 horrible shots.
And, baseball players aren’t the only ones who do “silly routines.” Most golfers, of all levels, have some strange ritual they do before they hit a shot. Same goes for basketball players on the foul line. Regardless, I don’t see what any of that has to do with using statistical data to help predict future performance.
As for your claim that “basketball players don’t say, ‘the rim looks bigger right now,’” here’s a quote from Lebron James earlier this year:

"I just felt like I was out there by myself," said James, who has scored at least 30 points in the second half of two of his last three games. "Everything was going right for me and I just felt like I was out there in practice. The hoop felt like the ocean."

Blogger Gabe Feldman -- 9/10/2008 10:37 PM  


Rick--

To provide a little more scientific support than a quote from Lebron James, a psychology professor at Purdue apparently just published a study that looked at the relationship between perception and performance in golf. According to the study:

"Golfers have said that when they play well the hole looks as big as a bucket or basketball hoop, and when they do not play well they've been quoted as saying the hole looks like a dime or the inside of a donut."

Blogger Gabe Feldman -- 9/10/2008 10:54 PM  


Gabe,

Perhaps you are right that it depends on the level of play you're talking about. [I can't relate to those feelings in basketball or football, but then again I didn't play those sports past the high school level.] But let's just assume for sake of argument that the psychological component is the same in other sports (but I'm still not sure about), I guess the question still exists as to whether a statistic is a good indicator to measure future performance. There are too many tangible and intangible variables impacting a player's performance that make it difficult for me to accept that any statistic, which is based entirely on past performance, is useful in predicting future performance, especially over the long term in projecting a player's ability to perform at an elite level.

Blogger Rick Karcher -- 9/11/2008 6:27 AM  


Rick-

Adjusting for BABIP is not a new concept in sabermetrics. Now, what you need to understand is that these projections are not concrete "this player is going to hit this for sure" statements. This is a terrible misconception that drives a lot of the angst toward sabermetrics that people seem to have.

Whatever number that comes from the projection equates to the midpoint of a reasonable range that one would expect a player to hit given the available information. The more relevant information available, the narrower the range. So, a player coming from Japan, or a player one year into the major leagues would have a much wider range than a player with an established record.

The article you linked by Ron Shandler is a very basic boiled down explanation of what someone making a projection will do. In estimating batting average, one would estimate various components - BB%, K%, FB%, HR/FB, and BABIP and come up with a projection. I'll spare you the details beyond that.

The amount of data utilized in a lot of these projections - the best in my opinion being PECOTA, a complex projection system used by the BaseballProspectus.com team - is huge. They are generally very accurate because the models have been built using 140 years of data.

My roundabout point is that I definitely think you're looking at these projection models (and likely sabermetrics as a whole) the wrong way. They're not be-all-end-all statements as to how a player is going to do. Rather, they are projections that indicate a range of expected performance.

There will always be outliers, and there will always be external factors that throw some projections off. However, dismissing a science because it doesn't jive with your anectotal perception of how sports work is nothing short of foolish.

Anonymous Mark DeVincentis -- 9/11/2008 3:08 PM  


That's o.k., I've been called worse things than foolish. And FYI, it's anecdotal, not anectotal.

Blogger Rick Karcher -- 9/11/2008 8:58 PM  


It's a typo. My points still stand.

Anonymous Mark DeVincentis -- 9/12/2008 11:19 AM  


Regarding "foolish" (since you wanted to take it to heart and get a little defensive)...

My point is that clearly you don't really understand the point behind these projection systems. Therefore, your dismissing them altogether without much knowledge of what they entail is foolish.

This is true of anything. If you don't know much about something, you shouldn't make sweeping dismissive statements about it. That is foolish. Surely you agree?

Anonymous Mark DeVincentis -- 9/12/2008 11:28 AM  


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