Arizona State University's #CurtainofDistraction: Is there an effect on free throws?

Update 2/13/2015: Thanks to Justin Wolfers, this blog post ended up on The New York Times. A question I've received was "Why do your stats and Wolfers' stats differ?" Simply put, there's more than one way to skin a cat -- or in this case, stats a Sun Devil. You can see in this post that I use four different approaches to assess the Curtain of Distraction. Dr. Wolfers also uses his own methods for statistical analyses. All are up to interpretation. Enjoy!

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The Curtain of Distraction is quite literally a curtain at Arizona State University men's basketball games that is strategically placed behind the away team's basket. When the away team shoots free throws, the curtains open revealing a cast of characters in costumes doing as much as they can to distract the free throw shooter.

Sound familiar? The movie BASEketball had this exact same concept.

The only difference: ASU is actually doing this in real life, at real NCAA basketball games.

But does it work? I mined free throw data from Sports Reference from ASU's home games this season and ran some stats to see if there is indeed evidence to say the Curtain of Distraction is... well, distracting.

From merely eyeballing the data, signs point to yes.

Thus far, ASU has hosted 14 home games.

11 of the 14 teams have a lower free throw percentage (FT% = free throws made/free throws attempted) at the ASU game than any other away game.

There are two big discrepancies in the eyeball analysis:

  • Some teams that have lower FT% are simply a mere 1% lower (on the other hand, Oregon State was almost 40% lower at ASU than at other away games this season!). In stats, this would be a problem with variation in data -- aka variance.
  • Some teams just didn't shoot many free throws -- sample size is an issue when looking at the single game at ASU versus all the other away games combined. Like trying to compare a day to a year, it's just not an easy or logical comparison.

The best way around issues of variance and sample size would be to compare all the teams who played at ASU as one averaged number. That would increase the amount of free throws taken (increasing sample size) and would also help bring the variance down (the general rule of thumb for variance is the larger the sample size, the closer you will be to the true variation of your data).

So I ran comparisons on free throw percentage on teams at ASU, at other schools, whether the away team beat ASU, and whether the team lost to ASU.

From the most simple analysis: The Curtain of Distraction isn't distracting.


Figure 1. No significant difference in FT% when playing at ASU or at any other school as an away team. Y-axis is FT%; error bars are standard error of the mean.

Statistically speaking, there is no difference between playing as an away team at ASU and playing as an away team at any other school. Even though 11 of 14 schools had lower FT% at ASU than at other schools, and even the data in the chart above show FT% for away teams at ASU shoot 62% while shooting nearly 70% at other schools, the variance (about +/-3%) is high enough to say there really isn't a difference in the data.

So I broke these data into teams that won at ASU versus teams that didn't win at ASU and ran the analysis again.

Looking at only ASU home games, Curtain of Distraction may be a winning component

Figure 2. Teams that lose at ASU shoot almost 9% lower at ASU than on the road at other schools (F(1,24)=5.73, p<.05)

Figure 2. Teams that lose at ASU shoot almost 12% lower that teams that beat ASU. (F(1,24)=5.73, p<.05, ηp2=.193, BF10=2.69)

When I isolate just the the ASU home games, the data indicates teams who lost at ASU had a lower FT% than teams that won at ASU -- to the tune of about 12% difference.

Now, there are some logical explanations for why teams lose if they don't shoot free throws well that don't include the Curtain of Distraction. The most simple explanation is: if you don't score points, you are more vulnerable to losing. Shooting and making free throws increase your score. If you don't convert free throws then you don't generate points. Lower FT% would indicate a lack of point generation and therefore an increased losing probability.

But what if you are playing well in the basketball game but just aren't doing well at shooting free throws? On average, ASU allows 16 free throw shots. That's 16 "free" points. That's a large amount of points to "not do well" on and still win. One team, Lehigh, shot free throws poorly (56%) but still beat ASU. In total, they still made 13 free throws.

What about teams who shoot free throws well but lose? Out of all the teams who came into ASU and lost, only one team shot above 70% at the free throw line: Pepperdine shot 80% (12 FTs made) and still lost. Three teams shot 60-67% (no team shot above 67% other than Pepperdine), 8 teams shot less than 60%.

When you look at teams who came in to ASU and won versus teams who came into ASU and lost, The Curtain of Distraction may very well be a factor

Figure 3. Teams that lost at ASU had worse FT% at ASU than at any other schools this season (F(1,24)=6.09, p<.05, =.202, =3.19)

Figure 3. Teams that lost at ASU had worse FT% at ASU than at any other schools this season (F(1,24)=6.09, p<.05, ηp2=.202, BF10=3.19)

Is there something about ASU that makes losing teams shoot worse? There very well may be. Teams that lose at ASU shoot almost 10% worse at the free throw line than at any other schools this season.

You would assume that FT% should be relatively the same across venues. In fact, that's definitely the case for teams that beat ASU -- they shoot basically the same at other schools. But in the case of teams that lose at ASU, 10% is a very large difference. In terms of likelihood, there is a 73% chance that your team will lose if you shoot free throws poorly.

How much of that 73% is due to The Curtain of Distraction? Hard to say. Again, multiple factors play into what causes a miss at the free throw line -- performance under pressure, ability to shoot from that distance, personal health, personal energy level...

But I would go out on a limb to think The Curtain of Distraction isn't helping you shoot any better. Unicorns making out and twerking? How would that not break your concentration?

So does The Curtain of Distraction distract?

I've presented four ways to look at the performance of teams at the free throw line when playing at ASU. Three of the four ways show results in favor for the idea that ASU's venue -- whether it is The Curtain of Distraction or otherwise -- has an intangible that decreases the free throw percentage for away teams.

If we exclude the eyeball results and only include the three statistical tests, two of these three statistical analyses favor the idea that ASU's venue is particularly different than other venues this season. You can say The Curtain of Distraction plays a large role -- or plays little-to-no role -- but the fact is that ASU's environment is a hard one to play in.

If you do, however, believe in the most simple analysis -- which says there is no difference for free throws at ASU versus any other venues this season -- then you do have a strong argument against the Curtain of Distraction. That particular analysis is truly asking is there something that affects all teams -- win or lose -- when shooting free throws at ASU? And the answer just based off that statistic is No. There is no difference.

If there were to be a definitive effect of The Curtain of Distraction, it should influence teams who lose against ASU and also teams who win against ASU. The Curtain of Distraction antic happens against all opponents; you can't selectively say Oh, The Curtain of Distraction is going to work today against Oregon State but in two days against Oregon let's just do it for funsies. That's not how distractions work.

I personally am a huge fan of it and wish very much to believe it to contribute towards this 73% losing correlation. Whether there is actually a substantial affect is difficult to say, but we can definitely say two things: 1) there's no way it is helping the other team and, 2) it is pure hilarity and amazing.

9 thoughts on “Arizona State University's #CurtainofDistraction: Is there an effect on free throws?”

  1. Greg says:


    1. Nick Wan says:

      Always seem to mess that up. Thanks!

  2. Mike Rothstein says:

    Is the curtain only at one end, the end where road teams shoot in the 2nd half? If so, have you done any comparison of 1st half vs, 2nd half FT%? Samples start to get pretty small at that point, at least on a per-game basis, which makes it harder to conclude anything, but without distinguishing between halves, we're not really isolating the effect of the curtain.

    1. Nick Wan says:

      From the games I've watched, it appears on both ends. But the only games I get to see are ESPN/ABC games -- maybe it's different when it's not an ESPN game?

      Good idea though, I'll look into it.

      1. Johnathon says:

        Hey I'm part of the group that does it and just wanted to clarify that the Curtain is only used during the second half when the opposing team shoots into the student section. We do keep track of first half vs second half FT stats and last I knew it was around 70% in the first half and 60% in the second I believe. Thanks for the article and support! I am a data analytics major myself so I love this type of analysis!

        1. Nick Wan says:

          Thanks for the clarification Johnathon! Maybe when the season is all wrapped up, I'll do a follow-up.

          1. Johnathon says:

            Yeah absolutely! Just let me know.

  3. Jack Lavelle says:

    A most imaginative development. Go Devils! Let's see how far it gets us in the PAC-12 tournament. We don't have to worry about anything after that, since we ain't going to the Big Dance. That stinks. I don't want to get started on sportswriter and NCAA bias.

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