Run differential and you: a love story


Editor's note: this "HookSlide classic" post originally appeared at Bless You Boys on May 27, 2015

If you're anything like me, the idea of advanced metrics appeals to you, but the thought of doing real math is a major turn-off. For me, the threshold is simple: if the equation can't be easily solved while also bonging a beer, I'm not interested.

Run differential just happens to be one of those advanced metrics that can be understood, and quite quickly and easily translated into something useful (predicting future win/loss records) without having to come within 20 feet of a cosine. (Whatever the hell that is.)

Run differential itself is just a matter of basic subtraction. Take the number of runs a team has scored, subtract the number of runs the team has allowed, and now you have their run differential. This can be used later to get a discount on parking when attending home games.

(If even this amount of math is giving you the shakes, you can always just use Google to find a web site that shows each team's run differential. ESPN is one such site.)

At the time of this writing, the Tigers have a run differential of +13 (200 runs scored, 187 runs allowed). Now, what to do with this information? (Hint: do not attempt to impress the bartender with it, unless you want to get charged for drinks you didn't order.)

The true stats geeks have figured out that roughly 10 runs equals one win. So here's the trick: start with a .500 win total (or 50 percent, if you prefer) , convert that run differential to wins, and add it all together.

The Tigers have played 46 games, so 50 percent (or a .500 win record) would be 23 wins. That +13 run differential, divided by ten, becomes 1.3 extra wins, giving them a projected win total of 24.3 -- round down to 24, of course, unless you really want to get thrown out of that bar.

The run differential gives us an idea of how many wins the Tigers should have, and at the moment, they actually have 26 wins, so they are outperforming their projection just a bit. That can mean they've gotten lucky a couple of times, it can mean they've just performed well in low-scoring games, or it can mean their run differential is skewed by a few blowout games.

To project what the Tigers' record should be at the end of the season if their run differential remained the same, just do the same bit of math starting with 50 percent of 162 games, or 81 games. That's it, really. That's the big secret. Take the run differential, divide it by 10, and add that number to a .500 win record.

It works in reverse, too. If you can just remember that 81 wins is the baseline, you can easily figure out where a team needs to be to get to, say, 91 wins. They need to pick up ten extra wins above .500, and if one win is equivalent to ten runs, then the team needs to be around the +100 mark for run differential. This is also a very effective way of calculating, with relative precision, how much you should be laughing at the Chicago White Sox right now. (That -56 run differential would drive Hawk crazy, if he knew what run differential was.)

There are caveats, of course. Especially early in the season, a couple of blowout wins or losses can skew the run differential. The Toronto Blue Jays, for instance, have a +26 run differential, and after 47 games, that means they should have about 26 wins. They don't. They're currently in last place with a 21-26 record, and if you're a Blue Jays fan, you should definitely bring this up with the manager in a loud and belligerent manner the next time you're sitting near the dugout.

The reason, more than likely, is the fact that they've had about eight games this year in which they scored 10 or more runs, and several more in which they've scored seven or eight runs. That would explain the discrepancy in run differential and actual win/loss record. Or it could be the metric system. (If you're Canadian and are offended by this joke, I meant it in good fun, and I accept your apology.)

Another thing that could potentially make the numbers less than accurate is the fact that the whole idea of "10 runs equals one win" is what you'd call a (... wait for it ...) "ballpark" figure. I guarantee that if you ask a true stats geek about it, you'll get a very lengthy answer about how that number needs to be adjusted regularly for league averages, occasionally weighted for linear scalability and non-linear polar attraction, and calculated to the seven zillionth decimal point for optimum precision.

But you will not even hear this last part of the explanation.

You will be busy bonging another beer.

Questions for Discussion:
  1. If John gets a 4-foot lead off first base and breaks for second at an initial burst-speed of 20.7 feet per second, and the pitcher throws a curve ball at 72 mph, how likely is this question to turn into an algebra problem?
  2. The 1987 Twins had a run differential of -20. Do you need any more proof that they are Satan's Offspring?
  3. Can it be my turn to use the bong, or are you just going to hog it like a stupid hogging pig-hog?
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