Thursday, August 26, 2004

Poor Sabermetrics

Every once in a while I come across an article that reminds me how important it is to be careful with how we use numbers to evaluate the performances of baseball players. Tom Alexander's new column at Chicago Sports Review is one such article.

Alexander's thesis is that because a walk is as good as a hit, OPS undervalues walks since it gives a player credit for singles in both on-base percentage AND slugging percentage but only credits the player for walks in on-base percentage. "Let’s think about this for a second, though." writes Alexander. "Obviously in most cases a walk is as good as a single."

Alexander does not even attempt to convince us of this, which is strange, since it seems obvious to me that a walk is not as good as a single. A walk can only advance baserunners who are forced to the next base; a single can advance baserunners as far as their legs can carry them. A single can score a man from second; a walk cannot. With the bases empty, a walk is as good as a hit, but with runners on, a single is clearly better. That is why OPS is good at explaining how much a hitter contributes to his team, despite the fact that walks and singles are counted differently.

Alexander continues: "There needs to be a new very basic statistic that is simply (BB+HBP+TB)/(BB+HBP+AB)." (The parentheses, which are pretty clearly needed, were added by me.) Why do we need such a statistic? I'm not saying we don't need it, just that it's still not clear that we do. What explanatory or predictive value would such a statistic have?
Here, finally, Alexander's findings might amount to something, even if I'm not sure what it is. He christens his new statistic "Alexander Rating" or "AR." (Oh boy. I'm going to pretend that's named after Grover Cleveland Alexander.) He then lists the players whose 2004 AR rankings are much higher than their OPS rankings. The list includes Jose Valentin, Mike Cameron, Carlos Delgado, Chipper Jones and other guys who have lots of walks and low batting averages.

Alexander writes, "Ultimately, though, Batting Average, and even OBP is a poor measure [sic] of what they bring to the team, because their real value comes in the idea that when they get a hit, it's a big one." But what about all the outs these guys chew up in the process?

Next there's a list of guys whose OPS rankings are far higher than their AR rankings. The list includes Ichiro, Michael Young, Johnny Estrada, Lyle Overbay and other guys who've gotten a lot of singles this year. Alexander: "I'm not saying that they're not having great seasons, but in certain cases, OPS is a bad measure of how good of an offensive player someone is, particularly when juxtaposed with AR."

Alexander doesn't give any actual reasons for this, but in a certain sense he may be right. AR has, as far as I can see, zero explanatory value - walks simply aren't as good as singles. But it may have some predictive value, in that I'd bet a lot of guys on the second list - the ones whose value is heavily concentrated in singles - are going to take steps backward next year. Singles are much more likely to fluctuate greatly from year to year than walks or power.

Still, the premise upon which Alexander's study is based - that a walk is really as good as a hit - is the sort of counterintuitive and wrong kind of thinking that makes non-sabermetric types of fans throw their hands up and think it's all snake oil.

Thanks to Baseball Primer for the link.

6 Comments:

Blogger Rowdy said...

It cracks me up when writers name new statistics after themselves.

5:27 PM  
Blogger Charlie said...

To his credit, after I posted this, Alexander did come on Primer and claim that he was just kidding about the name. But yeah, it's pretty much the height of arrogance.

12:52 PM  
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