A man had a fear of flying. His main worry was that there could be a terrorist on board carrying a bomb. For the last 15 years he had managed to avoid travelling by air. However one day he had no choice to travel to a conference by plane. Since he was a statistic professor, he used his mathematical skills and came up with a logical solution.
He was calm as he packed and head toward the airport. When he passed the security check, they discovered a bomb in his carry-on-baggage. The police hauled him off immediately for interrogation.
“This is strange!” the interrogating officer exclaimed. “According to our records, you’re an accomplished scientist, a caring family man and an active member of your church. Why do you want to blow up an airplane?”
“I’m sorry”, the professor replied. “There must be a misunderstanding. I never intended to blow up the plane.”
“So, what on earth prompted you to bring a bomb on board?!”
“Let me explain. I’m a statistics expert and according to my statistical calculations, the probability of a bomb being on an airplane is 1/1000. That’s quite high if you think about it. It’s so high that I would have severe anxiety on a flight.”
“And what does this have to do with you trying to bring a bomb on board of a plane?”
“You see, since the probability of one bomb being on my plane is 1/1000, the chance that there are two bombs is 1/1000000. If I already bring one, the chance of another bomb being around is actually 1/1000000, and I feel much safer!”
This popular math joke illustrates that at times what seems logical and common sense may not be an answer to a problem. The solution of the anxious professor was based on logical calculations of mathematical probabilities and statistics. However its effects become a self-fulfilling prophecy. The very action of the professor that tried to avoid the danger exacerbates it.