IMAGINE you are on a TV game show. The charismatic game show host puts his arm around your shoulder and points you in the direction of three closed doors.
Behind one door, he informs you, is a brand new Ferrari. But behind the other two doors is a far less desirable mode of transport, a donkey. He asks you to pick a door.
Number three has always been your lucky number. So after a sufficiently dramatic pause, you make your decision and go with door number three. Sensing the growing suspense in the audience, our host decides to prolong your agony further. So instead of making the big reveal by pulling back door number three, he opens door number one. To your relief, you see one of the two donkeys. Gasps all around. You are still in the game. The Ferrari is either behind door two or three.
Now the game-show host offers you this deal. You can stick with your original decision and stay with door number three, or you can switch over to door number two. What would you do? If you are like the vast majority of people, you’d probably assume that there is no advantage to be gained in switching from your original decision. So you stick with lucky number three.
Big mistake! By switching from your original choice, you actually increase your chances of winning the Ferrari from 33pc to 66pc.
If you find this solution to be counter-intuitive, take solace in knowing that some of our greatest mathematicians have also struggled to identify the optimal move in this situation. This brainteaser is better known as the Monty Hall problem, named after the host of the American game show ‘Let’s Make A Deal’. But be warned, posing the Monty Hall problem while sitting on the high stool is likely to incite confusion, dissention and ultimately lead to your isolation.