[Don Pearce[_3_]]

On Wed, 18 May 2011 08:44:57 -0500, "David"
wrote:

"Don Pearce" wrote in message
...
The host acts as a leak of information. It might help to imagine
an
alternate game, where the host does not know the contents of the
doors,
and the game is void if the host reveals the car. This version
puts you
back to 50/50 when the host reveals a goat, whether you switch
doors or
not.
***
Not true. When the host reveals a goat whether he guessed or
knew
it was there makes absolutely no difference. You should still
switch doors.

David


If the host does not know, he might quite as easily reveal the
car.
You then can't win it. Do you guarantee yourself 2/3 odds by
switching
then? No. If the host reveals a goat by chance, the odds do
indeed
drop to 50/50.

d
***
Sorry, I disagree. Yes the host could reveal a car if he is
unaware of the situation. If this happens, the game was defined
as void. If the host instead reveals a goat, there is no
difference whether he guessed or knew the goat was there.

David



Void is not one of the permitted outcomes. Suppose the host
accidentally revealed the car - to be equivalent to the intentional
goat revelation, he would then have to say "never mind, take the car
anyway". That would leave you in the 1/3 2/3 situation. If he reveals
a goat by chance the game degenerates to the simple situation - the
host has chosen one of the three, and you get to pick between the
remaining two, always assuming that he did not pick the car.

The point of the intentional revelation is that by switching you get -
in effect - both doors, not just the one.

d