"Arny Krueger" wrote in message
news
"Trevor" wrote in message
u
"spamtrap1888" wrote in message

...
The player picks a door and has a 1/3 chance of being
right. This chance does not change when a losing door is
revealed, so the only remaining choice gives you a 2/3
chance.

Which totally ignores the fact that the only reason the
first door is opened is because the host already knows it
is incorrect. This is NOT a purely statistical game of
chance, the host can manipulate the odds either way, and
regularly do.

There are two iron rules that dictate which door the host opens.

(1) There can't be a car behind it

(2) It can't be the door the contestant picked.

If the contestant picks a door with no car, then there is only one other
door the host can choose. The host has no choice and can't affect the
outcome.

If the contestant chooses a door with a car, then the host can choose
either
of two two doors that have no car, but which one he chooses doesn't seem
to
affect the outcome. His effect on the odds comes from the fact that he
revealed one of the two doors with no car behind it.

How can the host manipulate the odds?

Correct. The host has no effect on the odds.

Part of the confusion occurs because people confuse permutations and
combinations. In the situation where the contestant has chosen the good
prize, the two bad prizes form a combination, not a permutation.