Anita conducts a survey to determine if Americans are willing to support the arts by contributing money directly to local theater groups. One night she and her assistants interview five hundred people who are attending a performance of a musical at the city’s biggest theater. To help ensure random selection, they purposely select every other patron they encoun-ter for interviewing. There is only one interview question: “Are you willing to support the arts by giving money to local theater groups?†Ninety-four percent of the interviewees answer yes. Anita later reports that a large majority of Americans are willing to support the arts by giving money to local theater groups.
A prominent sociologist wants to determine the sexual attitudes of women aged twenty-five to forty-five. The main question to be explored is whether heterosexual women in this age group feel satisfied with their partners’ sexual performance. The sociologist interviews two hundred of her friends who belong to the target group. She also asks two hundred of her female colleagues at her college to complete and return a survey ask-ing the key question. She gets 78 completed surveys back from women in the target group. She finds that 75 percent of all the interviewees say that they are not satisfied with their partners’ performance. She concludes that most heterosexual women aged twenty-five to forty-five aren’t happy with the sexual performance of their partners.
Exercises 8.4, Number 5
- For the following argument, indicate which conclusions from the ac-companying list would be strongly supported by the premise given. Assume that all statements are true.
Number 5: Seventy-seven percent of adults interviewed in three Philadelphia shopping malls (650 people) say they will vote Democratic in the next presidential election.
a. Most people will vote Democratic in the next presidential election.
b. Seventy-seven percent of adult residents of Philadelphia will vote Democratic in the next presidential election.
c. Many people in Philadelphia will vote Democratic in the next presidential election.
d. A substantial percentage of people who shop at malls in Philadelphia will vote Democratic in the next presidential election.
Exercises 8.8, Numbers 1, 3, 4, and 6
- Analyze each of the following causal arguments. Identify the conclusion and whether the argument appeals to the method of agreement, the method of differ-ence, the joint method of agreement and difference, or correlation. In some cases the conclusion may be implied but not stated. Indicate whether the argument is strong or weak.
Numbers 1: Forty-five patients were admitted to Mercy Hospital for pneumonia in December. They were all given standard treatment for pneumonia. After five days, thirty of them were well enough to go home. The other fifteen, however, somehow acquired other infections and were not well enough to be released for fourteen days. The only relevant factor common to these fifteen is this: They all stayed in the same ward (different from the ward that the other group stayed in). Something about staying in that ward is the cause of the prolonged illness.
Numbers 3: “An experimental vaccine prevented women from becoming persistently infected with a [type of human papillomavirus called HPV-16] that is associated with half of all cervical cancers, researchers reported. . . . The study involved 2,392 women from 16 to 23 years in age. Participants were randomly assigned to receive three shots of either an HPV-16 vac-cine or a placebo (a dummy substance). The study was double-blinded—that is, neither the investigators nor the study participants knew who got the vaccine and who got the placebo. Participants were followed for an average of 17 months after getting the third shot. . . . [Forty-one] women developed HPV-16 infection—all of these women were in the placebo group. . . . By comparison, no one who got all three vaccine shots devel-oped an HPV-16 infection.†[National Cancer Institute]
Numbers 4: Getting the endorsement of the teachers union in this town is absolutely es-sential to being elected to the school board in this city. No one has ever won a seat on the school board without an endorsement from the teachers union.
Numbers 6:
In Instance 1, when factors X, Y, and Z were present, E happened.
In Instance 2, when factors X, Y, and P were present, E happened.
In Instance 3, when factors X and Z were present, E did not hap-pen.
In Instance 4, when Z and P were present, E did not happen.
Instance 5, when X, Z, and P were present, E did not happen. Therefore, Y caused E.
Exercises 8.10, Numbers 5, 8, and 10
- For each of the following causal statements, indicate whether the specified cause is:
(a) a necessary condition
(b) a sufficient condition
(c) a necessary and sufficient condition
(d) neither a necessary nor a sufficient condition.
Numbers 5: The mighty Casey hit the ball out of the park, winning the game by one run.
Numbers 8: Johann got a good grade on the exam because he studied the night before.
Numbers 10: Simone lost weight by exercising regularly.
Sample Solution