On a Game show, a contestant is faced with a choice of three closed doors, behind two of which are goats and behind the other is a Ferrari. Trying to win the Ferrari the contestant selects a door.
Before opening the chosen door the host opens one of the other two doors, revealing a goat. The host then asks the contestant if she would like to change her selection or keep the one she has already chosen.
What should she do to maximise her chances of getting the Ferrari – keep the door she’s already chosen or change to the other unopened door, or does it not matter?