3.66 Subscribers to a local newspaper were asked whether they regularly, occasionally, or never read the business section and also whether they had traded common stocks (or shares in a mutual fund) over the last year. The table shown here indicates the proportions of subscribers in six joint classifications.

Traded Read Business Section Stocks Regularly Occasionally Never Yes 0.18 0.10 0.04 No 0.16 0.31 0.21

a. What is the probability that a randomly chosen subscriber never reads the business section?

b. What is the probability that a randomly chosen subscriber has traded stocks over the last year?

c. What is the probability that a subscriber who never reads the business section has traded stocks over the last year?

d. What is the probability that a subscriber who traded stocks over the last year never reads the business section?

e. What is the probability that a subscriber who does not regularly read the business section traded stocks over the last year?

3.67 A corporation regularly takes deliveries of a particular sensitive part from three subcontractors. It found that the proportion of parts that are good or defective from the total received were as shown in the following table:

Subcontractor Part A B C Good 0.27 0.30 0.33 Defective 0.02 0.05 0.03

a. If a part is chosen randomly from all those received, what is the probability that it is defective?

b. If a part is chosen randomly from all those received, what is the probability it is from subcontractor B?

c. What is the probability that a part from subcontractor B is defective?

d. What is the probability that a randomly chosen defective part is from subcontractor B?

e. Is the quality of a part independent of the source of supply?

f. In terms of quality, which of the three subcontractors is most reliable?