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Monday, October 17, 2011
Visualizing wOBA
This is how I like to visualize the various components of wOBA. Here’s what to look for:
1. The green area under the 1.000 line is equal to the green area above the 1.000 line. This implies that the average value of the events equals 1. This forces wOBA = OBP.
2. The gap in the red area gives you the value of each event above the 0.333 baseline (or whatever the league average OBP is). This gap is exactly proportional to the Linear Weights run values.
Because of these two points, you get the wOBA values, of roughly 0.7 for a walk, 0.9 for a single, 1.3 for a double/triple, 2.0 for a HR. That’s all there is to it.
There are two great implications of using wOBA:
A. Even though wOBA IS Linear Weights, I have never ever ever had to explain what a “negative run value” is. It just doesn’t exist in wOBA. It’s hidden by having the baseline lowered as I have.
B. Because it is coupled with OBP (the same mean, and the same denominator of plate appearances), and OBP is perfectly suited for the binomial distribution, wOBA takes on similar characteristics. Not exactly, but close enough for our purposes. Whereas the binomial would say p*(1-p), in this case, we’d use p*(1.1-p).
Hence, my love for wOBA.