On Wed, Dec 05, 2007 at 04:59:42AM -0500, Richard Prosser wrote:
> To my mind, provided the host acts the same whether or not the correct door
> was initially selected,  then there are only 2 possible outcomes. 

The host does not act the same. That's where the probability shift occurs.

The host knows where the car is. So he will never reveal the car. That
means that his behavior changes depending on if the car is selected
initially or not.

1. If you pick the car, then he shows you 1 of the 2 goats.
2. However, if you pick a goat, he cannot show you the car! So he must
eliminate the other goat. And that's all the difference.

>The odds  are then 50-50.

It's 67/33 for switching. See my 1 door, 2 door picking posts elsewhere for
a clearer explanation.

BAJ
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