Originally Posted by The Unfan

Switching improves the odds of winning. Let us assume you pick box 1. The number of the box you picked doesn't matter but it helps explain the reasoning. If you pick another box just swap 1 with the number you chose and you'd get the same result.

If the car is indeed box number 1 than you could reveal either 2 or 3. However if the car is in 2 you have to reveal 3 and if the car is in 3 you have to reveal 2. 2 out of 3 times you had to reveal a specific box, and in those cases the switch is the win. 2 out 3 times you should switch.