A fair coin is flipped 90 times. What is the probability that more than two-thirds of the tosses result in tails?If needed, use the z-table to answer the question.

Two-thirds of 90 is 60, so “more than two-thirds” means more than 60 tails. For a fair coin, the number of tails has mean 90(0.5) = 45 and standard deviation √[90(0.5)(0.5)] ≈ 4.74. The z-score for 60 is (60 − 45)/4.74 ≈ 3.16, whose upper-tail probability is about 0.0008. Thus the probability is approximately 0.0008, choice B.

AI-written and checked against the verified answer.