Question

. A study of seat belt users and non-users yielded the randomly selected sample data summarized in the table below. Number of Cigarettes Smoked per day 0 1-14 15-34 35 and over Wear Seat Belts 155 28 43 6 Don’t Seat Belts 159 24 46 11 (a) What is the probability that a randomly chosen subject does not wear seat belts and smokes more than 35 cigarettes a day? (b) What is the probability that a randomly chosen subject does not smoke given the subject wears a seat belt? (c) What is the probability that a person in the study who does not smoke wears a seat belt? (d) What is the probability a randomly chosen subject does not smoke or wears a seatbelt?

Answer 1

we have data

a)

the probability that a randomly chosen subject does not wear seat belts and smokes more than 35 cigarettes a day

=11/472=0.0233

b)

the probability that a randomly chosen subject does not smoke given the subject wears a seat belt

=155/232 =0.6681

c)

the probability that a person in the study who does not smoke wears a seat belt

=155/472 =0.3284

d)

the probability a randomly chosen subject does not smoke or wears a seatbelt

=P(wear seat belt)+P(does not smoke) -P(wear seat belt and does not smoke)

=(232/472)+(314/472)-(155/472)

=391/472

=0.8284