Sunday, November 16, 2008

JQAS: a rudimentary examination of ball-strike counts

A new issue of JQAS came out recently, and there's a baseball paper in it called "Slugging Percentage in Differing Baseball Counts," by Tharemy Hopkins and Rhonda C. Magel.

The paper compares slugging percentages on various ball-strike counts. Rather than just downloading a bunch of Retrosheet data and figuring it out, the authors watched games on TV. Those games took place between March 20, 2008, and April 20, 2008 (which means they must have included spring training games?), and led to the classification of 1260 at-bats (the authors say 1260 games, but that's obviously an error).

Rather than give the results for all possible counts, the authors divided the data in to "pitcher's counts," "batter's counts," and "netural counts". They did this by "communicat[ing] with 24 individuals who have had extensive baseball experience, including coaches, players, umpires, and sports writers." Eventually they settled on 0-0, 1-1, 2-1, and 3-2 being neutral counts, 2-2 being a pitcher's count, and all others being batter's or pitcher's depending on whether there were more strikes or more balls.

Their results for the 1260 at-bats were:

.5109 SLG in 505 neutral-count AB
.3233 SLG in 566 pitcher-count AB
.5753 SLG in 189 hitter-count AB

These numbers add up to exactly 1,260, which suggests that the authors considered only the count in which the AB was resolved. As has been noted many times, this is less useful than counting the results when the plate appearance *passes through* that count, regardless of where the count eventually ended up.

Because of the small sample size, the authors found no significant difference between the neutral count and hitter's count, but did find a difference between neutral and pitcher's count.

I believe there have been many studies that have examined the implications of ball-strike counts in more detail with larger sample sizes. One of mine is on page 4 here (.pdf). Let me know of any others and I'll add more links here.

UPDATE: Tom Tippett study here, courtesy Studes in the comments. Also see Tango's second comment for a few more links.

Labels: , ,


At Monday, November 17, 2008 6:27:00 AM, Anonymous Anonymous said...

Tom Tippett wrote a seminal article about this several years ago:

At Monday, November 17, 2008 10:15:00 AM, Blogger Tangotiger said...


I remember Phil's article, and it was great. The Tippett article as well.

I summarized the Tippett data on my blog

Post 6 in that blog entry has a link to a great Craig Burley article.

Post 16 also has a great piece.

Dave Smith at Retrosheet has a good piece last year (should be on their research page).

Another win for informal peer review.

At Wednesday, December 31, 2008 5:38:00 PM, Anonymous Anonymous said...

Greetings, this is Tharemy Hopkins, co-author of the mentioned article. I'm glad I looked around to find if anything was written on it. I get a computer generated message from JQAS letting me know how many people download it, but I never recieved any sort of feedback.

This was a senior project that I did for my Capstone class for my bachelor's degree in Statistics from North Dakota State. I presented a (required small) report on my "study" and spoke about my findings. We were to collect our own data and do simple tests on information we felt interesting. My passion is baseball.

After my presentation, the co-author advised that it could be publishable material. Working together, the paper you see on the JQAS web-site is what resulted. (And I did mention several times the games/at-bats error, although it was never corrected.)

Reading your response, I realize that recording the outcome of each count within the at-bat would have been better. At the time, that did not occur to me. I thank you for your comments, and will definetely look into your referenced articles.

On a perhaps unrelated topic (Mr. Tango, I know of your book), how did you get into what you do now? I am fresh out of college, and have been working for an insurance auditing firm for 6 months, but still have that "giddy, reach-for-the-stars" mentality when it comes to chosing a job/career. I have always wondered how sabermetricians got into their jobs, or what they do on a daily basis. I'm sure you hear that all the time, but I am very curious. my email is if any of you would spare a thought.

Thanks to all for your time.

Tharemy (TJ) Hopkins

At Monday, March 23, 2009 4:24:00 AM, Anonymous Anonymous said...

This comment has been removed by a blog administrator.


Post a Comment

<< Home