978-1259690877 Chapter 11 Part 2

IM – 11 | 13

9. Cause: strong muscles

Exercise 11-28

[A = A causal statement is used as a premise; B = A causal statement is used as a conclusion; C

= A causal statement stands by itself as an unsupported claim.]

1. ▲A

2. A

3. C

4. ▲C

12. B

13. ▲B

14. C

Exercise 11-29

[P = paired unusual events principle; C = common variable principle; COV = covariation

principle]

IM – 11 | 14

Education.

3. C

4. COV

17. P

18. ▲P

19. P

20. COV

21. P

Exercise 11-30

Note: Though the instructions point out that “there is not necessarily a correct answer,” the

hypotheses that seem better are listed below. We provide more detail with the “triangled”

answers from the text.

1. ▲Answers (b) and (d) seem better in that one can at least see how their being true could

IM – 11 | 15

Education.

could reduce death by stroke.

5. All seem equally plausible.

Exercise 11-31

[A = this may well just be coincidence; B = the stated “cause” might really be the effect, and the

stated “effect” might really be the cause; C = the “cause” and “effect” might actually both be the

effects of a third thing; D = legitimate cause and effect]

1. ▲C (Mowing the grass results in both fumes and grass dust.)

2. B

10. ▲B (Maybe smart people eat more fish.)

11. B

12. C

13. ▲B (If there is more violence, there is likely to be more on TV.)

IM – 11 | 16

21. B

22. ▲A (Coincidence)

Exercise 11-32

Here are some suggestions or hints. Churchgoers are less likely to use tobacco; they are less

Exercise 11-33

1. ▲Ways it can happen; possible outcomes

Exercise 11-34

1. ▲No. After the first draw, the remaining deck is smaller.

2. .5 x .5 x .5 x .5 = .0625, or 6.25%

3. .5 or 50%

IM – 11 | 17

Exercise 11-35

First, notice that Lungren’s argument is an IBE, an inference to the best explanation. An

Exercise 11-36

What is called for ideally is a side-by-side comparison of classes that are identical in all relevant

respects except that in one class, attendance is required, and in the other, it isn’t. In the real

Exercise 11-37

a. Identify a causal hypothesis that might be raised by the passage.

b. Identify whether the passage reports on a randomized controlled experiment, a prospective

observational study, or a retrospective observational study.

1. ▲(a) Poker players’ confidence in the strength of their cards causes differences in arm

motions that can be interpreted by observers who are not poker experts. (b) This is a

IM – 11 | 18

Education.

2. (a) Piano instruction produces better performance on ratios and fractions. (b) We can’t tell

if it’s a true controlled experiment because we don’t know if the kids were divided into

3. We’ll summarize here (the details are obvious from the question itself). We can’t say with

4. ▲(a) The lead ophthalmologist thinks that leaving a light on at night deprives infant eyes

of the rest needed for nonmyopic development. In short, the causal hypothesis at issue is

5. This is a presumably randomized experiment that attempts to show that coffee grounds

suspended as sediment in coffee cause headaches. Unfortunately, the members of the

IM – 11 | 19

Education.

experimental group knew they were mixing coffee grounds into their pudding. This is

enough to give us headaches. The argument gives only weak support to the conclusion, in

our opinion.

6. (a) and (b) This randomized experiment is designed to test whether curcumin suppresses

made.

7. ▲(a) The causal hypothesis at issue is that exercise prevents colds. (b) Presumably this is a

randomized controlled experiment, although the report does not specifically state that the

subjects were randomly divided into two groups; and one part of the experiment is a

8. This huge randomized experiment was designed to test whether taking aspirin every other

day reduces the risk of heart attack. Because of the large numbers, the percentages can be a

little misleading. Out of the experimental group and the control group respectively, 104

IM – 11 | 20

Education.

9. (a) The South African, French, and Canadian studies are retrospective studies. The

Southern Illinois–Florida State study is a randomized experiment. (b) The hypotheses

tested were that cigarette smoking causes (vascular-associated) impotence and that nicotine

causes an immediate reduction in sexual arousal. (c) and (d) The South African study

10. ▲(a) High doses of androgen lower high density lipoprotein (HDL) levels in the blood. (b)

This is a prospective observational study. (c) There are two comparison groups: the sixteen

11. First study: The hypothesis is that vasectomies don’t cause disease. It’s a prospective

study. Over 10,000 men were in each of the groups (with and without vasectomies). Given

12. The causal hypothesis is that radiation-induced tumors are prevented by dietary restrictions

in rats exposed to high doses of X-rays; this is a randomized experiment. Forty-four rats

IM – 11 | 21

Education.

are in the experimental group; an undisclosed number are in the control group. The

difference in frequency of effect (no tumors) was 80 percent (80 in the experimental group

versus 0 in the control group). The study strongly supports the hypothesis.

13. ▲(a) Cheating creates more positive feelings than guilty feelings. (b) This is a controlled

experiment. Its design does not require randomization except in the initial selection of

14. Causal claim: A behavior modification program aimed at Type A individuals prevents

heart attacks. The study is a randomized experiment. The experimental group consisted of

592 out of 862 predominantly male victims of heart attack; they were given group

counseling to ease Type A behavior. The matched control group consisted of 270 subjects

who received only cardiological advice. After three years, 7 percent of the experimental

group had suffered another heart attack, compared with 13 percent of the control group.

Exercise 11-38

1. The dog was reportedly more accurate than the standard PSA test, which surely is better

than chance at predicting whether an individual has prostate cancer.

Exercise 11-39

IM – 11 | 22

1. While prostate surgery may reduce your chances of dying of prostate cancer, it is not likely

to prolong your life. (The figures are compatible with a large number of people in the

surgery group dying on the operating table from their prostate surgery. That’s one way not

to die of prostate cancer.)