The probability a person is infected by certain cold virus is 0.2.

Question

If a random sample of 12 people is taken, what is the probability that at least one person will be infected by the cold virus?

(A) 0.2062

(B) 0.9313

(C) 0.2400

(D) 0.0687

Answer 1

1 - P(0) = 1 - (1-.2)^12 = .9313

The Expected value is .2 * 12 = 2.4. The Poisson approximation e^-2.4 would have easily led you to the right choice.