Lesson 23: Texas Sharpshooter

Spot the Faulty Logic #

“Look at these sports statistics! I correctly predicted the winner in 8 out of 10 games last month!” (But they actually made predictions for 100 games and are only showing the ones they got right.)

Discussion: Talk with your teacher about this example. What’s being hidden here?

How/Why It’s Often Used #

The name comes from a joke about a person who shoots randomly at a barn wall, then paints a target around the bullet holes and claims to be a sharpshooter. They’re finding a “pattern” after the fact, not actually demonstrating skill.

Our brains naturally look for patterns - it’s how we make sense of the world. But this can lead us astray when we focus only on the “hits” (data that fits) and ignore all the “misses” (data that doesn’t). It’s closely related to cherry picking, but specifically involves finding patterns in randomness.

Texas Sharpshooter in Action #

Did you spot the faulty logic? #

If you make 100 predictions, you’d expect to get many right just by chance. Highlighting only the 8 out of 10 correct ones (while hiding the other 92 predictions) creates a false impression of predictive ability.

Second Example #

“This psychic is amazing! She predicted that something significant would happen to me this month, and look - my car broke down!”

The Flaw #

“Something significant” is so vague that almost anything could count as fulfilling the prediction. The prediction wasn’t specific enough to be meaningful, and the “pattern” is being found after the fact.