In case you missed the first 3 parts of “Playoffs are a Crapshoot”, here they are:
In the previous installment, we estimated the Bradley-Terry rating for the playoff teams. While these are the best estimates we can make using only the 2019 head-to-head results, they overstate the strength of the strongest teams. This is because of the phenomenon (often discussed here with respect to player results) of regression to the mean.
Baseball win records are the result of skill and luck. Before we can intelligently discuss regression to the mean, we need to be somewhat more careful about what we mean by this.