Wednesday, May 12, 2004

The news here just keeps getting worse. Another personnel carrier exploded today. I don't have the stomach for politics; I need some positively sophomoric distraction.

For me sophomoric distraction means one thing: baseball statistics. In recent years a great many people who need to get a life have invented various new stats meant to measure in one number the value of a hitter (or pitcher). Almost all fail to take into account the crucial fact of baseball: the expendable currency of baseball is not at-bats but outs. In other words, a team does not get a fixed number of at-bats but rather a fixed number of outs. So production needs to be measured in terms of outs made by a hitter (or gotten by a pitcher). Once that is understood, there are two basic characteristics that a good "universal" stat must have:
1. It's ingredients should be the kind of stuff you keep around the house (such as in your daily newspaper).
2. It should correlate with the number of runs a hitter is worth per game. Roughly speaking, that means it should approximate the number of runs a team would score if it consisted of nine copies of this guy.

Here is about the closest your going to come to a stat satisfying those criteria:

NOPS = (SLG/1-BA) + (OBP/1-OBP)
(where SLG=slugging pct.; BA=batting avg.; OBP=on-base pct.)

Note that SLG + OBP is your basic OPS. The difference here is the denominators which normalize by outs made. (NOPS stands for normalized OPS.) Here are a few key facts about NOPS:
1. The major league average over the past 30 years has been consistently extremely close to 1.0. So the scale is perfect: an average ballplayer is at 1, and a good/bad ballplayer is above/below 1.
2. NOPS correlates really well with runs scored. Over a season, the number of runs a team scores per game is very very close to 6.7*NOPS - 2.4. No other stat I know of has as good a correlation (but another very good one is 6*OPS/(1-OBP) - 2). Obviously, then, we can use the same formula to evaluate individual players. Clearly this fails at the extreme since, for example, a hitter batting .000 will be worth -2.4 runs which makes no sense. But it's really not bad. An average hitter (260 BA, 330 OBP, 395 SLG so NOPS = 1.02) would be worth about 4.4 runs per game, which is about right. Barry Bonds in his steroid phase is worth something over 12 runs per game.

OK, back to grisly reality. The news is starting.

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