1. Public Onion reported that 5% of Americans are afraid of being alone in a house at night. If a random sample of 20 Americans is selected, find the probability that there are at most three people in the sample who are afraid of being alone at night.
Answer: 98.4098472% ≈ 98%
2. In a music store, a manager found that the probabilities that a person buys a zero, one or two or more CDs are 0.3, 0.6 and 0.1 respectively. If six customers enter the store, find the probabilities that one won't buy any CDs, three will buy one CD and two will buy two or more CDs.
Answer: 38.88% ≈ 39%
3. The probabilities are 0.25, 0.40 and 0.35 that an 18 wheel truck will have no violations, 1 violation or 2 or more violations when it is given a safety inspection. If eight trucks are inspected, find the probability that three will have no violations, two will have 1 violation and three will have two or more violations.
Answer: 6.0025% ≈ 6%
by: Marie Louissie Ynez U. Lavega
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