>I guess just including the probability in the original question would do it, after reading it over. It's easy to get sidetracked (as some apparently did) and consider the goat/door to be already open when you're weighing the odds, and treat the problem as one simple independent probability (which has the 1/2 solution) - but in fact, you're supposed to be comparing two different odds, one based upon the other - hence the term: "conditional" probability.
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>I see Jim Booth stated it well near the start of the thread...
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>I see Ken Matson just posted a link to M. vos Savant's famous column on this problem, as well as the also famous "loophole," perhaps more interesting than the original problem :)

Fair enough. As long as you agree that I'm right and your wrong. < s >

I've never even heard of the famous "loophole".