The Monthy Hall problem is a maths problem that is easy to understand but the solution isn’t so intuitive. The problem is as follows:
Suppose you’re on a game show, and you’re given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door. The host, who knows what’s behind the doors, opens another door which has a goat. He then says to you, “Do you want to switch?” Is it to your advantage to switch your choice?
In one study, only 13% of participants got it right. A huge proportion of the general public, in addition to some university academics with PhDs, also got the wrong answer.
The answer is to always switch, since it doubles your chances of winning the car.