A fair coin is tossed times. Let denote the number of heads obtained. What are the mean () and variance () of the random variable ?

Answer and explanation

Correct answer: B. and

  1. Step 1: follows a binomial distribution with parameters and ().
  2. Step 2: Mean is .
  3. Step 3: Variance is .
Answer
and .
Why not the others: forgets to multiply by ; divides the mean by 2; and assumes 100% success rate.

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