ERA+ Calculating incorrectly

ahemmer · 08-13-2010, 04:45 PM

Hello!

I was going through a couple of my relievers, and noticed the career ERA+ is calculating strangley. It appears that ERA+ is being calculated as a weighted average.

ERA+ *(innings pitched for year/career innings pitched) = ERA+ weight for one year. Each year is calcualted separately and then added to come up with a career ERA+. Normally this would be fine and good, but extremely successful cups of coffee (like a few innings, no runs given up) heavily skew the calculation.

For instance, one pitcher I have has a career ERA of 4.79 over 200 innings. The league average over that time is 4.52. however, his career ERA+ is 123. Versus the league average, I think his ERA+ should be about 95. He does play in a hitter friendly ballpark, but I don't know if the game adjusts for ballpark. Even if it did, I doubt the the ERA+ would be affected by that much. The player had a cup of coffee of 6 1/3 innings without giving up a run, which gave him an ERA+ of 999 for the year. Adjusting the 6 1/3 inning to league average lowered his ERA+ all the way to 95.

As another example, a closer in the most pitcher friendly park in the game has a 1.60 ERA over 174 1/3 innings. The league average ERA over that time is 4.17. His career ERA+ is 272, but should actually be more like 260 because a 22 inning, 3 runs allowed stint is weighted heavily.

I think the career ERA+ should be calculated against the league average ERA versus a weighted average. I have not checked to see fi OPS+ is calcualted the same way.

Thoughts?

TribeFanInNC · 08-13-2010, 05:05 PM

I haven't completely digested everything you said here, but a couple comments off the bat.

a) I believe ERA+ is ballpark weighted IRL. I assume it is in the game as well.

From the Hardball Times ERA+ definition:
"ERA measured against the league average, and adjusted for ballpark factors. An ERA+ over 100 is better than average, less than 100 is below average.

b) The 999 notation is basically infinity for that pitcher. Since he has given up 0 runs, he is infinitely above the league average.

Admittedly I don't know how career ERA+ should be calculated. Time for some research.

08-13-2010, 04:45 PM	#1
ahemmer Minors (Rookie Ball) Join Date: Jul 2008 Posts: 24	ERA+ Calculating incorrectly Hello! I was going through a couple of my relievers, and noticed the career ERA+ is calculating strangley. It appears that ERA+ is being calculated as a weighted average. ERA+ *(innings pitched for year/career innings pitched) = ERA+ weight for one year. Each year is calcualted separately and then added to come up with a career ERA+. Normally this would be fine and good, but extremely successful cups of coffee (like a few innings, no runs given up) heavily skew the calculation. For instance, one pitcher I have has a career ERA of 4.79 over 200 innings. The league average over that time is 4.52. however, his career ERA+ is 123. Versus the league average, I think his ERA+ should be about 95. He does play in a hitter friendly ballpark, but I don't know if the game adjusts for ballpark. Even if it did, I doubt the the ERA+ would be affected by that much. The player had a cup of coffee of 6 1/3 innings without giving up a run, which gave him an ERA+ of 999 for the year. Adjusting the 6 1/3 inning to league average lowered his ERA+ all the way to 95. As another example, a closer in the most pitcher friendly park in the game has a 1.60 ERA over 174 1/3 innings. The league average ERA over that time is 4.17. His career ERA+ is 272, but should actually be more like 260 because a 22 inning, 3 runs allowed stint is weighted heavily. I think the career ERA+ should be calculated against the league average ERA versus a weighted average. I have not checked to see fi OPS+ is calcualted the same way. Thoughts?

08-13-2010, 05:05 PM	#2
TribeFanInNC Hall Of Famer Join Date: Oct 2007 Posts: 4,019	I haven't completely digested everything you said here, but a couple comments off the bat. a) I believe ERA+ is ballpark weighted IRL. I assume it is in the game as well. From the Hardball Times ERA+ definition: "ERA measured against the league average, and adjusted for ballpark factors. An ERA+ over 100 is better than average, less than 100 is below average. b) The 999 notation is basically infinity for that pitcher. Since he has given up 0 runs, he is infinitely above the league average. Admittedly I don't know how career ERA+ should be calculated. Time for some research.