Texas Sharpshooter Fallacy

The “Texas sharpshooter fallacy” is based on a story about a person who comes to Texas and sees bullet holes in the side of a barn, with a bull’s-eye circle drawn around each hole. The person goes in search of the marksman, who, when found, admits that he simply shot at the barn and drew the circles later. The fallacy has been used in medical research, where clusters of data might be meaningless, just like the shots and circles of the Texas “sharpshooter.”
 
The “sharpshooter” story has been cited in print since at least 1977 and 1982, although it didn’t specify Texas as the location. Dr. Seymour Grufferman, of Pittsburgh, used the story in “Clustering and aggregation of exposures in Hodgkin’s disease,” Cancer (volume 39, 1977). The name “Texas sharpshooter effect” was used in 1982, “Texas sharpshooter fallacy” was used in 1992 and “Texas sharpshooter problem” in 1995.
 
 
Wikipedia: Texas sharpshooter fallacy
The Texas sharpshooter fallacy is an informal fallacy in which pieces of information that have no relationship to one another are called out for their similarities, and that similarity is used for claiming the existence of a pattern. This fallacy is the philosophical/rhetorical application of the multiple comparisons problem (in statistics) and apophenia (in cognitive psychology). It is related to the clustering illusion, which refers to the tendency in human cognition to interpret patterns in randomness where none actually exist.
 
Etymology
The name comes from a joke about a Texan who fires some shots at the side of a barn, then paints a target centered on the biggest cluster of hits and claims to be a sharpshooter.
     
Google Books
Jewish Currents
Volume 31
1977
Pg. 31:
“Along the road he stopped at a village to rest his mount. He sat down under a tree—and right there in front of him was the side of a big barn. He couldn’t believe his eyes. That whole side of the barn was covered with little circles, drawn with chalk, and in the center of each circle was a bullet hole! He jumped up in amazement. Who is this sharpshooter around here who never misses? Maybe they could have a little contest while he was here.
 
“So he knocked on the door of the farmhouse and asked if they knew who the marksman was. Yes, they did. They brought him a barefoot boy of about twelve. ‘Here he is, Your Excellency, our son the sharpshooter!’ Of course, the prince was surprised. He asked the boy, Tell me, young fellow, how do you manage to hit the bullseye all the time? Here, look at all these medals. I’ve just finished five years of training and even I couldn’t hit the target every single time.’
 
“‘Oh,’ said the boy, ‘there’s nothing to it. I just like to shoot. So I shoot at the side of the barn and then I take the piece of chalk and draw a circle around the hole.’”
 
Google Books
Cancer Epidemiology and Prevention
By David Schottenfeld and Joseph F. Fraumeni
Philadelphia, PA: Saunders
1982
Pg. 744:
Another difficulty in evaluating clustering is the “Texas sharpshooter effect.” (...) Such a posteriori clusters are analogous to the story of the Texas sharpshooter who would shoot his rifle at the side of a barn and then carefully draw a target around each bullet hole so that the bullet hole passed exactly through the center of the “bull’s-eye”.
 
Google News Archive
22 October 1982, The Courier (Prescott, AZ), “A stand for standards” by Larry Provence,  pg. 3B, cols. 4-5:
I once read a story of an army sharpshooter who visited a small town. He was amazed to find targets drawn on trees, walls, fences and barns. Even more fascinating was the fact that each target had a bullet hole in the exact center of its bull’s eye.
 
Inquiring about this, he had the honor of meeting the remarkable marksman. “I’ve never seen anything like this in my entire career,” said the Army man. “It’s incredible! How did you do it?”
 
“Easy as pie,” replied the local rifleman. “I shoot first and draw the circles afterwards.”
 
Google Books
Life in the Shadow:
Living with Cancer
By Bill Soiffer
San Francisco, CA: Chronicle Books
1991
Pg. 58:
One difficulty in evaluating clusters is known as “the Texas sharpshooter effect.” Critics say the after-the-fact connections made in cancer clusters remind one of the story of the Texas sharpshooter who (Pg. 59—ed.) shoots his rifle at the side of a barn and then carefully draws a bull’s-eye around each bullet hole. For scientists cancer clusters tend to be code words for unproved and unscientific findings that are unworthy of pursuit.
 
Google Books
Epidemiology and Control of Neural Tube Defects
By J. Mark Elwood, Julian Little, J. Harold Elwood, et al.
New York, NY: Oxford University Press
1992
Pg. 248:
It can be difficult to establish whether there is an aetiological connection between the cases, or whether the cluster represents the ‘Texas sharpshooter’ fallacy. As described by Grufferman (1982), the Texas sharpshooter first shoots at the side of the barn, and then paints the target, with the bullseye centred on the bullet hole! In addition, the number of cases in reported clusters is often too few to be informative.
 
New York (NY) Times
TELEVISION REVIEW; Power Lines and Cancer: Is There a Connection?
By WALTER GOODMAN
Published: June 13, 1995
(...)
Clever graphics demonstrate what critics call epidemiology’s Texas sharpshooter problem in action: the sharpshooter fires repeatedly at a barn door, then draws a circle around one cluster of shots as evidence of his accuracy, ignoring the many shots that hit elsewhere on the barn. The point is that sheer chance is always present in statistics.
 
13 April 1999, USA Today, “Cancer clusters are difficult to nail down” by Kevin V. Johnson, pg. 8D:
Reports are so numerous that experts have a name for false clusters: the Texas sharpshooter fallacy. The term refers to a hypothetical rifleman who fires several shots at a barn wall, then draws a bull’s eye around the shots. “Clusters can look pretty dramatic, even when there’s nothing there,” Kaye says.
   
Decision Science News
The Texas Sharpshooter Story
August 29, 2012
(...)
We have been looking into the roots of the Texas Sharpshooter vignette in academic writing. The earliest and most common “initial” cite we found after a quick search was Grufferman’s from 1977, with no claims that this is the earliest use:
 
Here it is.
 
There have been several dramatic time-space clusters of leukemia reported in which, following an initial observation of two or more cases in a locality, a time unit and geographical area are selected so as to best define a time-space cluster. Such a posteriori clusters are analogous to the story of the Texas sharpshooter who would shoot his rifle at the side of a barn and then carefully draw a target around each bullet-hole so that each bullet-hole passed exactly through the center of the “bull’s-eye.” Although a posteriori clusters do serve to demonstrate that cases can cluster in time and space, they do not allow for determining whether this is more than a chance occurrence.
-Grufferman (1977)

REFERENCES
Grufferman S. (1977). Clustering and aggregation of exposures in Hodgkin’s disease. Cancer 39, 1829-1833