Question
A fair coin is flipped four times. What is the probability that tails occurs exactly 3 times if it is known that tails occurs at least twice?
Answers
Reed
Where did you get this question from?
Reiny
The last part of the sentence " if it is known that tails occurs at least twice?" contradicts the first part.
ignoring that last part we would have:
C(4,3)(1/2)^3 (1/2)
= 4 (1/16) = 1/4
ignoring that last part we would have:
C(4,3)(1/2)^3 (1/2)
= 4 (1/16) = 1/4