[IBL] IBL Range Ratings

[Sean Sweda]

The primary data source for range ratings was changed to the Inside Edge  
data published on Fangraphs, as announced here:

https://lists.ibl.org/pipermail/members/2016-February/001551.html

Fangraphs UZR range runs (RngR) is also used as a secondary data source,  
primarily for validation but also because using it allows some in-season  
visibility given that the IE data is not synthesized by Fangraphs into an  
aggregated metric.

When the data source was switched the mapping methodology was also  
changed.  Plays made above/below average are converted into a runs saved  
metric and then mapped into a range rating based on the number of expected  
runs saved based on projected distribution of IFR/OFR plays.  For example,  
given the average expected distribution of IFR/OFR plays the difference  
between A (100%) to K (0%) range at 3B would be approximately 44 runs.   
That means in order to gain an A range a 3B would need to grade out over  
+20 runs per season.  For positions that have more plays (e.g. SS, CF) this  
number would need to be even higher.

Jace Peterson got a good range rating because he made 1/1 of plays rated  
"unlikely" by IE and 2/2 rated "even" by IE.  An "average" result would  
probably be about 1/3 of those plays.  When you pro-rate the runs saved  
from his 66 innings at 3B to a full season you get an very large value.   
This is pulled back down by combination with the secondary data source  
(UZR) and the capping mechanisms that are applied to low playing time  
players, resulting in "D".

My intention has been to create a detailed write-up on the blog, but I've  
only got so much time...

TLDR:
1) range is based on IE (and UZR), UZR is a decent approximation in-season
2) A/B ratings are very rare now
3) small sample size "flukes" are mitigated but still exist


Sean