7.3.1. In Action
This is a famous demonstration of how hard we find it to work out probabilities. When it was published in Parade magazine in 1990, the magazine got around 10,000 letters in response92% of which said that their columnist, Marilyn vos Savant, had reached the wrong conclusion.2 Despite the weight of correspondence, vos Savant had reached the correct conclusion, and here’s the confusing problem she put forward, based roughly on the workings of the old quiz show Let’s Make a Deal presented by Monty Hall.
Imagine you’re a participant on a game show, hoping to win the big prize. The final hoop to jump through is to select the right door from a choice of three. Behind each door is either a prize (one of the three doors) or a booby prize (two of the doors). In this case, the booby prizes are goats.
You choose a door.
To raise the tension, the game-show host, Monty, looks behind the other doors and throws one open (not yours) to reveal a goat. He then gives you the choice of sticking with your choice or switching to the remaining unopened door.
Two doors are left. One must have a goat behind it, one must have a prize. Should you stick, or should you switch? Or doesn’t it matter?
This is not a trick question, like some lateral thinking puzzles. It’s the statistics that are tricky, not the wording.
Taken from : Mind Hacks
