note tilly This will be my one and only contribution to this thread, I have seen the Monty Hall problem too many times.<P> The situation where switching makes sense is if (as in the original problem) the announcer actually knows which door has the prize, and the announcer will always pick a door without the prize first. Then your analysis is correct. After the announcer shows you a losing door, your chance of winning if you switch is 2/3, versus 1/3 if you stay put.<P> But if the announcer is an ignorant guesser, then it makes no difference whether you switch or not. This is the case that corresponds to most people's intuition - indeed the value of switching with the usual analysis is because the announcer affects the information available.<P> The third case, which [chipmunk] alluded to, is the case of an evil announcer who knows the answer and wants you to fail. In this case you should stick to your guns... 46229 46311