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Origin of the Texas Sharpshooter

The picture of the Texas sharpshooter is taken from an illustration by Dirk-Jan Hoek (CC-BY).

The infamous Texas sharpshooter fires randomly at a barn door and then paints the targets around the bullet holes, creating the false impression of being an excellent marksman. The sharpshooter symbolizes the dangers of post-hoc theorizing, that is, of finding your hypothesis in the data.

The Texas sharpshooter is commonly introduced without a reference to its progenitor.

For instance, Thompson (2009, pp. 257-258) states:

“The Texas sharpshooter fallacy is the name epidemiologists have given to the tendency to assign unwarranted significance to random data by viewing it post hoc in an unduly narrow context (Gawande, 1999). The name is derived from the story of a legendary Texan who fired his rifle randomly into the side of a barn and then painted a target around each of the bullet holes. When the paint dried, he invited his neighbours to see what a great shot he was. The neighbours were impressed: they thought it was extremely improbable that the rifleman could have hit every target dead centre unless he was indeed an extraordinary marksman, and they therefore declared the man to be the greatest sharpshooter in the state. Of course, their reasoning was fallacious. Because the sharpshooter was able to fix the targets after taking the shots, the evidence of his accuracy was far less probative than it appeared. The kind of post hoc target fixing illustrated by this story has also been called painting the target around the arrow.

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