Comments on: The Slash Stats

By: vivaelpujols

vivaelpujols — Tue, 13 Oct 2009 22:00:31 +0000

I agree with you that RJ didn’t put that very well. wOBA is better than OPS, but not because it correlates with team runs any better.

By: vivaelpujols

vivaelpujols — Tue, 13 Oct 2009 21:58:55 +0000

What exactly does that mean?

By: wobatus

wobatus — Tue, 13 Oct 2009 20:00:22 +0000

OPS components are less volatile than wOBA.

By: MPC

MPC — Tue, 13 Oct 2009 15:31:44 +0000

Yeah. It’s supposed to be a rough measure of power, but triples aren’t an indicator of power, they’re more of an indicator of speed.

By: Patriot

Patriot — Tue, 13 Oct 2009 14:01:20 +0000

Aweb wrote: “OPS is basic arithmetic with numbers based on how many bases an event is worth in the game, which is observable to anyone who watches the game (i.e. – a double worth twice as much as a single).”

SLG is simple arithmetic based on the number of bases an event is worth. OBA counts each event that

OPS is simple only if you assume that OBA and SLG are already calculated for you. But if they are, you don’t ever see the value of each event isolated. In order to see how the events are actually weighted in OPS overall, you have to get rid of the different denominators, and you get something like:

((H+W+HB)*AB + TB*PA)/(AB*PA)

There’s nothing intuitive about OPS when you look at it through that prism. And the value of each event is not intuitive at all–it is intuitive for OBA as a standalone statistic and SLG as a standalone statistic, but not for OBA+SLG.

By: aweb

aweb — Tue, 13 Oct 2009 11:30:25 +0000

OBP=(BB+H+HBP)/(PA)
SLG=(4*HR+3*3B+2*2B+1B)/AB

OPS=OBP+SLG

That’s pretty easy even if it doesn’t really “make sense” to add the two together mathematically.

By: aweb

aweb — Tue, 13 Oct 2009 11:26:52 +0000

There’s no “calculus” involved in OPS at all. There are calculations, and algebra, but not calculus. Calculus involves derivatives and/or anti-derivatives.

I’m not sure how anyone can argue with a straight face that wOBA is simpler, at least in the calculation sense, than OPS. OPS is basic arithmetic with numbers based on how many bases an event is worth in the game, which is observable to anyone who watches the game (i.e. – a double worth twice as much as a single). As opposed to how many runs an event is typically worth in a game, which is not.

Somewhere I have seen the correlation on runs scored with a series of popular metrics of team hitting, BA, OBP, SLG, OPS, OPS+ and then the newer statistical measures (but I can’t find it). I seem to recall being very unimpressed, as I am here, by the small improvements in correlation over and above OPS. Aside from the rare player far from the normal OBP/SLG splits, OPS is just fine.

By: Jason

Jason — Tue, 13 Oct 2009 11:07:25 +0000

R.J., instead of the straight ONB + SLG for OPS, could you compare wOBA to a modified OPS (= 1.7697 * ONB + SLG)? I would be interested to see how this mOPS does against wOBA in your comparison of team production numbers versus runs scored.

There is a method behind the 1.7697; it involves using the correlation function and goal seek in Excel.

Thanks.

By: Colin Wyers

Colin Wyers — Tue, 13 Oct 2009 05:30:36 +0000

OPS is simpler than wOBA so long as you don’t actually think about what it’s doing. If you actually do the crunching required to pick apart what OPS is doing (hint: it’s a lot of calculus) you’ll quickly find it’s not actually simpler at all.

By: Colin Wyers

Colin Wyers — Tue, 13 Oct 2009 05:28:07 +0000

For the vast majority of teams, almost anything that makes a modicum of sense is going to have a high correlation. (From 1993-2008, the correlation between at-bats and team runs scored is .64. Simply looking at home runs gives you a .75 correlation. Home runs times at bats? .81 correlation!)

The reasons wOBA is preferable to OPS for individual hitter evalution have almost nothing to do with correlation with team run scoring over a two-year time period.