Birnbaum: Regressing park factors in baseball

From SABR member Phil Birnbaum at Sabermetric Research on April 15, 2020:

I previously calculated that to estimate the true park factor (BPF) for a particular season, you have to take the “standard” one and regress it to the mean by 38 percent.

That’s the generic estimate, for all parks combined. If you take Coors Field out of the pool of parks, you have to regress even more.

I ran the same study as in my other post, but this time I left out all the Rockies. Now, instead of 38 percent, you have to regress 50 percent. (It was actually 49-point-something, but I’m calling it 50 percent for simplicity.)

Read the full article here:

Originally published: April 16, 2020. Last Updated: April 16, 2020.