THE BOOK--Playing The Percentages In Baseball

Thursday, August 17, 2006

Is It Easier To Standout in a High Run Environment?

By Tangotiger, 07:54 AM

No!

Proof follows:

Let’s use an example. A guy has a wOBA of .200 (i.e, OBP of .200 and SLG of .240). His ERA will be 1.42. A league wOBA of .280 has an ERA of 2.83. In this case, his ERA+ is 199.

Now, how would this guy have done in a .340 OBP league? A .200 in a .280, using the Odds Ratio method, gives us a wOBA of .250. With me so far? A .200 OBP in a .280 league is equivalent to a .250 OBP in a .340 league. That’s the translation.

Now, a .250 wOBA has an ERA of 2.23. A .340 wOBA has an ERA of 4.39. 439/223 = 197

***

Odds Ratio Method is:

.200/.800 = O(P1) = p1
.280/.720 = O(L1) = l1
.340/.660 = O(L2) = l2

p / l1 * l2 = p2

In this case, p2 = .331, which translates to an OBP of .331/1.331 = .250

• Sabermetrics • Talent_Distribution

#1 Tangotiger (see all posts) 2006/08/17 (Thu) @ 08:00

Actually, if I was more careful with my rounding, I would have ended up with pretty much the exact same ERA+.

#2 Joe Arthur (see all posts) 2006/08/19 (Sat) @ 04:08

What am I missing here? This seems like a tautology. The point of the tranform you performed is to preserve the relative relationship to the different averages, so its no surprise that relative measures will remain constant

#3 Peter Jensen (see all posts) 2006/08/20 (Sun) @ 09:41

I think Joe is right. The Odds Ratio Method is based on the assumption that the condition (pitcher wOBA) is based in the general population at the same rate as the control population.

#4 Tangotiger (see all posts) 2006/08/20 (Sun) @ 19:25

The Odds Ratio method preserves the wOBA. It does not preserve the ERA. Obviously they go hand-in-hand, but I don’t see why we should have expected the relative relationship of ERA to league to have held.

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THE BOOK--Playing The Percentages In Baseball

Thursday, August 17, 2006

Is It Easier To Standout in a High Run Environment?

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