On context for statistics

By Jason Wojciechowski on August 26, 2011 at 8:30 PM

Eric Seidman at Fangraphs makes what some may consider an obvious point, but one that needs to be said every once in a while regardless: statistics must be taken in context. He provides the example of Angel Pagan, whose slash-line of .264/.324/.385 would represent about average on-base work and fairly well below-average power in 2005, but this year, is pretty close to average in both categories, as the league slugging has dropped from .414 to .391 in that time.

Seidman also mentions park, but in both league and park contexts, he's talking about a comparison to average. I would go farther, though, because with players substantially above or below a league average mark, it can be difficult to discern just how far above- or below-average that player is. Take Mark Teixeira's .515 SLG this season (also cited by Seidman). This is substantially above the American League's .404 mark. But how much above? "100 points" is not an answer, because what does that hundred points mean? Is a .515 SLG above-average, very good, excellent? Elite?

A percentile would be an acceptable way to answer this question. (Teixeira stands in the top 15% of the AL for SLG among qualified batters.) Standard deviations (or z-scores) could also be used if reading those is something that comes naturally to you.

There's also the issue of "what does it really mean translated to runs?" This is particularly true when citing things like wOBA or TAv or wRC+. If you tell me that Mark Teixeira's wOBA is .369, I don't have an intuitive sense of what that means, either on a percentile level or, more importantly, a runs per game level. If you replace Teixeira with Daric Barton, how many expected runs does this cost you over the course of 10 games?

Some of this is my anti-scaling bias (i.e. I'd prefer a statistic be presented to me in runs in the first place, rather than scaled to look like an on-base average or a batting average), but as I recognize that I'm in a small minority on that, I can only ask that analysts occasionally give us a reminder of what you're saying in terms of the statistic that, in the end, is what players are always driving toward.

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