Astros-Sign-Stealing-Analysis - Don Allen

Recently, Tony Adams did an exhaustive analysis of “bangs” during each of the 2017 Astros home games that he could obtain from video. He has kindly published those results at and welcomed analysis by others. Kudos and thanks to Mr. Adams for doing the hard work and making the data available.

While Adams shows various player analyses and others have done some detailed analysis of aspects of the data, I thought it would be useful to investigate the bottom line, that is how much the banging actually helped the Astros score runs. To do that, I simply plotted the number of bangs for each game versus the runs scored by the Astros in that game. Then, I performed a simple linear regression analysis  in Microsoft Excel to determine how much the banging helped the Astros score runs.

To be accurate, I wanted to negate any bias from “outliers” that is data points that would influence the results but are outside the norm and could be influenced by other things. However, I also wanted to include as many games as possible. Since the Astros were shutout twice, I picked 2 outliers since, if I picked only 1 outlier, the results could be influenced by which game I selected. So, I threw out the two highest scoring games and the two lowest scoring games so that one or two games would not bias the results. By the way, I also repeated the analysis with 5 games thrown out at both ends and ended up with almost identical results.

The figure below shows the results of the regression analysis. If the banging helped the Astros, the regression line would show a positive slope so that, more bangs would result in more runs scored. If the banging hurt the Astros, the regression line would show a negative slope so that more bangs would result in fewer runs scored. In fact, the figure shows that the regression line slope is almost exactly zero, meaning that the number of bangs had no impact on the number of runs that the Astros scored! This was a surprising result about which I comment more below.  But a simple look at the data shows that, in the games in which the Astros tipped at least 30 pitches, they scored fewer runs than their average in 13 of those 19 games (or 14 of 22 games if you include the outliers). 

Linear Regression

I have a good friend that was an Astros pitcher for several years and pitched about a decade in the big leagues. When I told him what I had found he thought it was crazy. It had to have helped given that anytime a hitter knows what pitch is coming then that hitter must have an advantage. I agree but only up to a point. Consider some of the following variables:

• Most pitchers have more than one off-speed pitch and thus knowing that the pitch is not a fastball does not tell the hitter exactly what pitch is coming.

• The Astros evidently had a code breaking scheme for deciphering the opponent’s signs, but this could be somewhat complex to use in real time. Thus, it is possible that many of the bangs were either too late to make a difference for the hitter (after all the hitter must process the sign and then prepare himself mentally for the pitch) or were possibly incorrect.

• As several players have pointed out, stealing signs by non-electronic means is common and thus all teams can switch their signs at a moment’s notice. This was especially true in 2017 when the catcher was not limited to the number of mound visits. Thus, many of the bangs may be been based on signs that had since been changed and hence incorrect.

• Some hitters may have been mentally distracted by the bangs and knowing when an off-speed pitch was coming and simply did not hit as well that way. Imagine waiting for a bang and, when not hearing one, wondering if that meant a fastball was coming or if perhaps the players could not decipher the sign in time. That would be distracting. Perhaps that is why some players relied on it much more than others according to Adams’ research. Some may have indeed hit worse when using the banging.

In the middle of 2018, the team stopped using the banging because they did not find it effective. Perhaps this data indicates that was true (while I have not read the article, Robert Arthur in a January 30, 2020 article in Baseball Prospectus concluded that the banging hurt the Astros as much as it helped them). However, it is also possible that the Astros moved on to a more sophisticated scheme that they thought would be more effective but, so far, no hard evidence exists that they did.

It would be interesting to go through each at bat and note the result for plate appearances when the banging occurred.  While a single bang on a pitch that was taken can affect the entire at bat and thus this exercise might be difficult, it would be interesting to at least determine the batting average for balls in play that occurred on pitches where there was a bang.  It would also be interesting to determine what percentage of bangs were actually accurate!

While this research indicates that the Astros did not score more runs as a result of the banging scheme, it was still against the rules and, as the Astros have admitted, they deserved punishment. Some have thought the punishment to be too harsh and others have thought it to be too lenient. As I have tried to explain to some of the boys I coach in high school baseball, “When you do something wrong and get caught, you are at the mercy of the judge and jury – so it is best not to do what you know to be wrong.”

** Thank you to Mitchell Allen and David Paul for offering their thoughts on this blog post.

Additional Reading

- Sign Stealing Website with Raw Data

- Arthur, Robert, Moonshot: The Banging Scheme Hurt the Astros As Much As It Helped Them, January 30, 2020

- Verducci, T., How The Rise of Surveillance Cameras Is Making Baseball's Biggest Problem Even Worse,, November 2, 2018 (this article indicates that several other teams were using methods similar to those of the Astros to steal signs through 2018  and specifically mentions the Dodgers - shouldn't Manfred investigate all teams for sign stealing during this period and not just the Astros and Red Sox?  After all, Hinch was punished because he knew video sign stealing was going on but did not do enough to stop it ... shouldn't the commissioner be held to the same standard?)

- Verducci, T., Exclusive: MLB Set to Pass New Rules Designed to Crack Down on Sign Stealing,, February 19, 2019 (this article makes me wonder: considering that the above article indicates that other teams were using video to steal signs in 2017 and 2018, were the Astros really punished for their deeds in 2019 and not for their deeds in 2017 and 2018?)

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