Finite Math: Probability & Percentages

Question

Wonder Widgets Inc produces  Midget Widgets (MW).. Their data shows that 2% of the output is defective. A sample of 25 MWs is taken.

(a) What is the probability that exactly two of this sample are defective?

(b) What is the probability that at most two of this sample are defective?

Answer 1

Binomial situation applies here and can use formula to compute binomial probabilities.

a) C(25,2) * (0.02)^2 * (0.98)^23 = 0.075

b) C(25,0) * (0.02)^0 * (0.98)^25 +

C(25,1) * (0.02)^1 * (0.98)^24 +

C(25,2) * (0.02)^2 * (0.98)^23 = 0.987