Question

A batch of 20 semiconductor chips is inspected by choosing a sample of 3 chips. Assume 10 of the chips do not conform to customer requirements. Round your answers to the nearest integer. a. How many different samples are possible? b. How many samples of 3 contain exactly one nonconforming chip? c. How many samples of 3 contain at least one nonconforming chip?

Answer 1

Answer:

A batch of 20 semiconductor chips is inspected by choosing a sample of 3 chips. Assume 10 of the chips do not conform to customer requirements.

a) Number of different samples = 20C3 =  $\frac{20!}{3!(17!)}$ =1140

b) 2 good and one bad chip

Number of samples = 10C2 * 10C1 = 45 * 10 =450

c) 2 good 1 bad + 1 good 2 bad + 3 bad

Number of samples = 10C2 * 10C1 + 10C1 * 10C2 + 10C3

= $450+450+120=1020$