I have a few baseball questions.
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How is a pitcher’s ERA computed?
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How is a player’s slugging percentage computed?
Thanks
- (Earned runs times nine) divided by innings pitched.
If Smith pitched 168 innings and allowed 67 earned runs he would have an ERA of (67 x 9)/168 = 3.59.
2. Total bases divided by at bats - the same as batting average except you use total bases, not hits. You get a total base for every base earned on a hit. So total bases is equal to all hits plus doubles, plus (2 x triples) plus (3 x home runs.)
Say Jackson went 140 for 500 this year. He hit 27 doubles, 5 triples, and 33 home runs. He has a slugging percentage of (140+27+10+99)/500 = .552 - easy as pie.
And there is a little refinement. Say Jones is pitching and has completed one out in the 5th inning. He has pitched 4-1/3 innings. Then the next batter singles, the next gets on on an error and the third guys gets an infield hit loading the bases.
A new pitcher is brought in who gives up a home run. The new pitcher is charged with the run scoring as a result of the home run. Jones gets charged with two runs for the men on base as a result of the hits when he left the game while the run by the guy on from the error is an unearned run. I think.
More or less true. It’s important to note that the penultimate man faced by Jones in David’s example is not an earned run, so despite the new pitcher giving up a grand slam, only three earned runs are awarded – the runs scored by the men who hit the two singles Jones gave up are charged to him, and the single home run by the reliever is charged against him.
Further, pitchers are charged with earned runs only for what would have scored prior to three outs of errorless play. Modifying David’s example – Jones begins the fifth by striking out the eighth and ninth batters in the lineup, they being the first two men he faces. He then pitches an outside pitch to the speedy leadoff batter, who connects with it poorly and dribbles an easy grounder to third. Unfortunately, the regular third baseman is out on injury, and the man playing third today is in there for his hitting, not his fielding. He mis-throws to first, and the official scorer awards the leadoff guy first on an error.
This whole situation flusters Jones, who works the next two men with outside pitches and they walk. The manager then pulls Jones and puts in the reliever, who as in the original scenario gives up a grand slam.
Total earned runs given up: one – the homer that is charged to the reliever. Errorless play would have made the leadoff man out at first to end the inning, so Jones does not get charged with the runs scored by the two men he walked.
The reason for the X9 in the initial formula, by the way, is a holdover from the “complete game” scenario – a pitcher giving up two, three, two, and four runs respectively in four nine-inning appearances would have an ERA of 3.0, for obvious reasons. But with pitchers pitching stints of 4 1/3 and 1 2/3 innings, equating it to a nine-inning outing by the multiplication of earned runs by nine (which would of course be divided again by a multiple of nine if he had pitched only complete games) gives an easy comparison figure. There is or was one active pitcher who had a single-season ERA of 108.0 in his records – in his sole major-league outing that season, he pitched a third of an inning and gave up four runs, was pulled and never used in the majors again that year.
And a correction of a slight error in my previous post – that 3.0 complete-game pitcher was supposed to have given up three, two, three, and four runs in those four games; I typed it backwards.
Another wrinkle in the ERA formula is that if a pitcher comes in and gives up a few runs without recording an out (see bullpens: Oakland A’s), their ERA for that game would be infinite.