A store has 80 modems in its inventory, 30 coming from source a and the remainder from source

b. of the modems from source a; 20% are defective. of the modems from source b; 8% are defective. calculate the probability that exactly two out of a random sample of ve modems from the store's inventory are defective.

The number of defective modems in the inventory is 20%⋅ 30 + 8%⋅ 50 = 10 (out of 80). Note that the number of defectives in the inventory is fixed, i. e., we are not told that there is 1 8 probability that a modem in the inventory is defective, but rather that exactly 1 8 of all modems are defective. The probability that exactly two modems in a random sample of five are defective is = 0.102