THE BOOK--Playing The Percentages In Baseball

Thursday, March 31, 2011

Precision is in the eye of the beholder…

In the book Short Hops, the authors criticize (actually dismiss) UZR because, among other things, the parameters are too imprecise.  For example, a batted ball is classified as hard, medium, or soft, but of course batted balls, in actuality, have some discreet speed, not to mention the fact that the 3-tiered classification is a judgment call by imperfect scorers.  As well, a ball that is recorded as landing 300 feet from home plate at angle 32 degrees may in fact have landed 310 feet at an angle of 35 degrees.  Similarly, in order to estimate the position of the outfielders, batters are classified into long, medium, and short fly ball hitters.  You get the point.

Now, while the authors have a point - that all of these classifications are approximate - does that really make them imprecise?

Let’s put aside the fact that in science, advances are often made with inputs that are approximations.  In fact, that may be the rule rather than the exception.

Rather than try and answer the above question, I want to pose a few more questions to illustrate my point.

Think about lwts, wOBA, OPS, or some similar all-encompassing offensive stat.  What are the inputs?  Singles, doubles, triples, etc.  Are these inputs precise?  Well, there is no judgment or approximation involved (other than errors).  They are what they are.

Now compare that to the UZR inputs for batted balls. The offensive events seem to be a lot more precise and no one would think of assailing wOBA or lwts on that front (that the inputs are imprecise).

Now, what if instead of using singles, doubles, etc., for the offensive metric inputs, we decided that we wanted to do better.  We correctly realize that for purposes of estimating true talent or formulating a projection, not all hits and outs are created equal (not even all walks or K’s are created equal) - there are bloop and bleeder hits and line drive outs, etc.

So we decide to try and figure out which batted balls are “true” hits, outs, etc., by using the speed of the batted ball, the location it is hit to, it’s trajectory, etc.  We are now doing exactly the same thing as UZR does, in terms of batted ball classification.

Suppose we do a pretty good job with this and we are confident that our new inputs are much better than simply using singles, doubles, triples, etc.  I think this is a reasonable scenario, and there are in fact some advanced offensive metrics that do something similar - and do not take the offensive events at face value.

Now let’s forget that anyone ever invented wOBA, lwts, OPS, etc., in their old format, using the traditional offensive inputs - singles, doubles, etc.  Instead we’ll pretend that these metrics were originally invented using the better offensive inputs, the ones that imply singles, doubles, outs, etc., from the recorded parameters of the batted balls (and perhaps the estimated positions of the fielders, depending on the base/outs/score, and the power and speed of the batter).

These should be much better metrics than the original ones.

How would people like the authors of “Short Hops” react to these metrics?  In the same way they react to UZR!  OMG!  How can you possibly use or trust a metric that uses all of these approximations, and inputs that are subject to the whims and biases of the scorers, parks, etc?  The inputs are way too imprecise for these metrics to be useful!

Precision is in the eye of the beholder!