Round-trip fallacy is the confusion of absence of evidence of something for evidence of absence of something.

The term was coined by Nassim Nicholas Taleb in chapter five of his book The Black Swan.^[1]

A person named Faulty took a nap yesterday on the railroad track in NewRochelle, New York, and was not killed.

After the nap he made a statement: *Hey, look at me, I am alive.

That is evidence that lying on train tracks is risk-free.* ^[1]

A doctor examined a patient for signs of cancer with a CT scan and after the scan said to the patient: *Stop worrying, we have evidence of cure.

There is evidence of no cancer, the scan is negative.* ^[1]