[luvgal]

i wonder would the probability of either switching or staying would be 1/2. if the host randomly picks the door between the two unchosen doors without knowing where the prize is. and if the host opens the unchosen door with the prize.. then the contestant lose.. but if the host opens the door with the goat then what is the probability of having the prize?
could anyone pls answer this question with proof..
thanx