math
posted by Katherine on .
you take a threequestion multiplechoice test.each question has four choices.you don't know any of the answers. what is the experimental probability that you will guess exactly two out of three correctly
please help me i am confused

right = r
wrong = w
so you want
rrw
rwr
wrr
each of the above has a prob of 1/4 x 1/4 x 3/4 = 3/16
so the prob of getting 2 out of 3 correct is 3(3/16) = 9/16 
that should have said:
each of the above has a prob of 1/4 x 1/4 x 3/4 = 3/64
so the prob of getting 2 out of 3 correct is 3(3/64) = 9/64