Taking Don Wheeler’s Class; MLB Batting Averages are Lower… So What?
As I mentioned in June, I'm in Knoxville this week to take four days of classes with Donald J. Wheeler, Ph.D. I've long admired Dr. Wheeler and his work and I was thrilled when he wrote the foreword to my latest book.
One lesson from Understanding Variation is to not overreact to a report about a single data point.
I recently saw this headline:
What do you think? Please scroll down (or click) to post a comment. Or please share the post with your thoughts on LinkedIn.
Don't want to miss a post or podcast? Subscribe to get notified about posts via email daily or weekly.
Comments and discussion on LinkedIn, including some “Wheeler-isms” I posted as comments to this post:
Here is the spreadsheet (XLS via Dropbox)
Another interesting discussion that could be had is in deciding where to determine when a process change has occurred. For example 1969 could be used as the start of a new period in the chart since MLB lowered the pitching mound in response to the perception that pitchers had an unfair advantage. Or 2003 with the publication of Moneyball and the shift in evaluating players that de-emphasized traditional statistics such as batting average. Or maybe 2008 as it was the first season after the publication of the Mitchell report. And of course there are other points such as expansion years and others that I’m sure I’m missing.
Good question on determining where a process changed. When doing a retrospective chart, you can see signals or evidence of shifts. And then you can ask, “What happened?”
Or you can say, “I know there were changes… did it appear to have an immediate effect?”
You’re right about that change in 1969, but I don’t see a signal in the chart there. The MLB batting average was indeed higher in 1969 compared to 1968, but it’s in the range of common cause variation – it appears to be noise.
“Moneyball” certainly started the trend of emphasizing On-Base Percentage over Batting Average. The chart suggests the last downward shift started in 2009. I doubt the drop in batting average was a result of the financial crisis or President Obama getting elected :-)
Here is a Run Chart that shows batting average and on-base percentage together. Visually, they look very correlated. The calculated correlation factor for 1950 to 2018 is 0.93 (where 1.0 is perfect correlation). The correlation from 2010 to 2018 is just 0.73, which maybe isn’t surprising with an increased emphasis on drawing walks (which increases OBP).
Here is that data in Excel if you want to play with it.
Thanks for sending the data along. I’ll try have to take a look at it. Although it’s fantasy football season and I’m knee deep in trying to figure out the signal and noise in the various predictions available for drafting players. :)
Update — the MLB batting average ended at .248 for the 2018 season… so far for 2019, the MLB total average is just a bit higher at .249. We might have to go to four decimal places to see if last season was a signal… but there certainly seems to be a change to the game where the attempt to hit more home runs is leading to lower batting averages.