wouter van ooijen wrote: > I wrote: > > You know up front that the host is going to reveal one of the > > "goat" doors, taking it out of play. Therefore, it's really a > > two-door game from the outset, and you have a 50% chance of > > picking the correct door. > > There's /no/ advantage in switching. > > -- Dave Tweed > > You are the one behind the quiz in CCI? Yes. * > I hope you are kidding! Yes, sorry, brain fart. Too many different things going on today. :-( Richard Prosser wrote: > It (now) looks to me like :- > If you never change - Odds are 1 in 3 > If you always change - Odds are 2 in 3 > If you randomly change - odds are half way between 1/3 & 2/3 = 1/2. I managed to confuse myself with the last case. When I began to think about how you would set up a Monte Carlo simulation of the game, I realized my mistake. See, now I know why so many people have trouble with this! If you pick randomly whether or not to swich, the odds associated with choices prior to that don't matter any more. If you always (or never) switch, then only the odds associated with the first pick matter. Another way to think about it is that if you pick a goat to begin with, the host's hands are tied -- he has no choice, he *must* show you the other goat, which means the car is behind the remaining door. This happens in two cases out of three. -- Dave Tweed * Actually, I'm the editor of the "Engineering Quotient" column, but I'm also the primary contributor, because I get very little in the way of outside contributions of material. After a hiatus of about 2.5 years, the column is coming back on a bimonthly basis starting with the January 2008 issue. If anyone wants to send me suitable puzzles or engineering problems, you will get credit in print, and you'll have my eternal gratitude, as well. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist