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Sunday, March 04, 2018

We X-Rayed Some MLB Baseballs. Here’s What We Found.

On top of the fact that the balls became bouncier as the core itself changed, previous research at FiveThirtyEight showed that they also became less air resistant. The decrease in drag is probably a result of a smaller, slicker baseball with lower seams. The change in air resistance could add an additional 5 feet to the travel distance of a fly ball. Combine all these factors together — a lighter, more compact baseball with tighter seams and more bounce — and the ball could fly as much as 8.6 feet farther.

Bored Posted: March 04, 2018 at 10:17 AM | 9 comment(s) Login to Bookmark
  Tags: general, juiced baseballs

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   1. A Baseball Fan Posted: March 04, 2018 at 05:19 PM (#5633525)
Am I wrong in thinking that a sample size of four old baseballs and four new baseballs does not seem to be sufficient to base these claims on?
   2. Walt Davis Posted: March 04, 2018 at 11:01 PM (#5633622)
Well, it would be nice if they reported the standard error ... which is likely to be substantial. (That is 8.6 feet +/- what?) But apparently you can't just get your hands on 500 official ML baseballs.

For those thinking 8.6 feet doesn't seem like a lot -- according to the article they estimate that would be a 25% increase in the number of HRs ... which seems crazy high to me but what do I know? They note HRs are actually up 47% compared to the low point of 2014.
   3. Endless Trash Posted: March 05, 2018 at 03:48 AM (#5633641)
Am I wrong in thinking that a sample size of four old baseballs and four new baseballs does not seem to be sufficient to base these claims on?


It depends, I think, on how much variance there is in the manufacturing of baseballs.

Given how many home runs were hit though, it should be easy for them to get their hands on more balls. Come on people, donate that ball you caught to science! Nobody is impressed by it sitting on your desk at work.
   4. The Interdimensional Council of Rickey!'s Posted: March 05, 2018 at 08:41 AM (#5633663)
For those thinking 8.6 feet doesn't seem like a lot -- according to the article they estimate that would be a 25% increase in the number of HRs ... which seems crazy high to me but what do I know?


I can't add anything to the question of sample size for the study, or how reliable the numbers they come up with are, but yes. And extra +/- 9 feet of flight would be huge. Especially on flyball outs into the dead pull alleys. The difference between 325 and 335 is an out vs three rows deep in the LF stands.
   5. McCoy Posted: March 05, 2018 at 08:51 AM (#5633666)
I believe, and in think the article mentions it, that baseball has more started saving and testing a lot of baseballs so they can actually look at this question honestly.

In looking at this question one of the things I've discovered is that in the past there was a ton of variance between baseballs. It does seem the more modern baseballs have tightened up the specs but as the article mentions the guts are still inconsistent over a period of time.
   6. Crispix Attacksel Rios Posted: March 05, 2018 at 10:29 AM (#5633721)
But apparently you can't just get your hands on 500 official ML baseballs.

What about that jackass who spends all season running in front of people to catch balls and thinks people are rooting for him? Go confiscate some from him.
   7. PreservedFish Posted: March 05, 2018 at 10:40 AM (#5633726)
For those thinking 8.6 feet doesn't seem like a lot -- according to the article they estimate that would be a 25% increase in the number of HRs ... which seems crazy high to me but what do I know?


So, 6105 HRs last year. Does that mean there are about 1,500 balls hit to the warning track? That's 50 per team per season, or about once every three games. That does sound plausible.
   8. Tom T Posted: March 05, 2018 at 01:03 PM (#5633870)
Am I wrong in thinking that a sample size of four old baseballs and four new baseballs does not seem to be sufficient to base these claims on?


Unlike my field (MRI), CT attenuation is measured relative to an absolute reference.

So...if they did all of the scanning on the same CT system, on the same day, using a common jig to hold the balls int he center of the bore, and (ideally) mixed the order of the scanning of the balls, the findings should be robust.

I would expect the 40% difference they got for the outer layer of the core to be well outside any normal measurement variance for a (good) CT system. (And USC ought to have some good ones.)
   9. Walt Davis Posted: March 05, 2018 at 03:31 PM (#5634029)
#8 -- you seem to be talking about measurement error. The earlier poster is talking about sampling variability. Even with no measurement error, 8 is a small sample and we would have little confidence that it is a "representative" sample of all baseballs ... especially since the baseballs weren't randomly sampled from the population. That estimate on the expected number of extra feet a ball would travel is a function of a number of other estimated parameters which means the variance on the feet estimate is some function of the sum of all those other variances and likely quite large.

Question being is it an estimate of 9 feet +/- 1 foot (really good estimate) or 9 feet +/- 8 feet (in which case it's kinda useless). Basically if we had a random sample of, say, 8 baseballs from 2014 and 8 from 2017 ... and the 8 from 2014 each had the exact same characteristics (resulting in 325 feet) and the 8 from 2017 all had the exact same characteristics but different from 2014 (resulting in 335 feet) then, even with a sample of just 8 from each year, we'd have pretty good confidence that the different iss real. On the other hand, if we have a non-random sample of 8 from 2014 and their expected flights range from 315 to 335; and 8 non-random from 2017 and their expected flights range from 323 to 347, then we first don't have that much confidence in the mean estimate for each year and then we have even less confidence in the estimate of the difference of those two means.

If there was also measurement error on top of that, we'd have even less faith in the estimate.

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