Statistics Probability

The mean and variance of a random variable X having binomial distribution are 4 and 2 respectively, then P (X = 1) is

  1. 1/4
  2. 1/8
  3. 1/16
  4. 1/32

Answer

np = 4

npq = 2

q = 1/2, p = 1/2, n = 8

p(X = 1) = 8C1 (1/2)(1/2)7

The correct option is D.