A manufacturer of cotter pin know that 5% of his product is defective. If he sells cotter pins in boxes of 100 pins find the probability that

a) 10 pins will be defective in the box
b) Not more than 10 pins are defective in a box

1 answer

prob(defect) = .05
prob(no defect) = .95

a) I read that as exactly 10 out of the 100
= C(100,10) (.05)^10 (.95)^90
= appr .0167, according to my calculator

b) unreasonable question, you would have to do
prob(exactly 0 defective) + prob(1 effective) + ...+ prob(10 defective)
If you feel like it, repeat the pattern I used in a)