Multiple choice

A coin is biased so that heads comes up thrice as likely as tails. For three independent tosses of a coin, what is the probability of getting at most two tails?

  1. 0.16

  2. 0.48

  3. 0.58

  4. 0.98
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D Correct answer
Explanation

P(H) = 3/4, P(T) = 1/4. At most two tails means 0, 1, or 2 tails. This is 1 - P(3 tails). P(3 tails) = (1/4)^3 = 1/64. Probability = 1 - 1/64 = 63/64 = 0.984375.

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