Monty Hall demo v1.0

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, say No. 1, 
and the host, who knows what's behind the doors, opens another door, say No. 3, 
which has a goat. He then says to you, "Do you want to pick door No. 2?" 

Is it to your advantage to switch your choice?