你对Monty Hall problem引申理解有误。原题里主持打开的不是你选的门，你对自己选的门里是车是羊仍然不清楚。

但每个门里是车的几率是1/3，假定你选门1，主持人打开门3，是羊，去掉门2门3ambiguity的1/2，因此门2是车的几率增加一倍。

所有跟帖： 

• Monty Hall problem如果问，你选了门1，主持人打开了门1，是羊，问门2里是车的几率是什么，答案是 1/2. 因为 -燕京十景- ♀ (0 bytes) () 09/30/2014 postreply 10:46:40

• I assume 主持人选了一扇里面 is considered as [the second door], the rest -ca981- ♂ (0 bytes) () 09/30/2014 postreply 10:52:12

• Probability measures uncertainty. What already happened is not u -燕京十景- ♀ (85 bytes) () 09/30/2014 postreply 10:57:51

• Sure enough what happened may change future probability, but you -燕京十景- ♀ (90 bytes) () 09/30/2014 postreply 10:59:56