Answer:
i would switch
Explanation:
your chance of picking the right door that has the grand price is 33.33% because 1 out of 3 doors has the prize and you have a 66.66% chance of being wrong.
*just know that the host will never reveal the grand prize first because then the tension of the game show is gone, etc *
after knowing the door that has a goat, are my chances of winning 50/50 (1 out of 2 doors) ?
no.
Always switch!
your chances are still the same as before (33.33%). like i mentioned the host won't reveal the grand prize first.
I will refer to 3 doors: X, Y, Z
So if your 1 out of 3 pick wasn't the money(you chose x), and the money is in, let's say door Y, then the host will reveal Z. If the money is in Z, the host reveals Y. IF you chose the money the first time (X), then the host can reveal either Y or Z. no matter what, you are still stuck in that initial 33.33% chance that you chose right the very first time. But if you switch, regardless of the prize, you are now in the 66.66% zone. you have actually doubled your chances of winning.
to think about it in another way, when you are being asked to switch, you are given a dilemma : do you want to keep one envelope of do you want both of the others? you already know what is inside one of them (the goat). But since the one that will be revealed won't have the money in it, the chances that the other envelope has the prize are twice as high.