What is number of defective balls in the pack?

Question

A manufacturer of halogen bulbs knows that 3% of the production of their 100 W bulbs will be defective. a).What is probability that exactly 5 bulbs in a carton of 12 bulbs will be defective?

Answer 1

P = Probability of being defective = 0.03

1-P = Probability of not being defective = 0.97

 

 

12 C 5 = the number of combinations of 5 defects out of 12

(P)⁵(1-P)⁷= the probability for a single combination of 5 defects out of 12

 

The probability of exactly 5 defects = (12 C 5)(P)⁵(1-P)⁷