For Exercise 6.1, see page 126; for Exercise 6.2, see page 129.
6.3 Does meditation reduce anxiety? An experiment that claimed to show that meditation reduces anxiety proceeded as follows. The experimenter interviewed the subjects and rated their level of anxiety. The subjects were then randomly assigned to two groups. The experimenter taught one group how to meditate, and they meditated daily for a month. The other group was simply encouraged to relax more. At the end of the month, the experimenter interviewed all the subjects again and rated their anxiety level. The meditation group had a greater decrease in anxiety than the group told to relax more. These results might be biased because
(a) subjects should have been blinded to what treatment they received.
(b) the anxiety ratings at the end of the experiment should have been performed by someone blinded to which treatment a subject received.
(c) this is not a matched pairs design.
(d) the experimenter failed to use proper blocking.
6.4 Effects of TV advertising. What are the effects of repeated exposure to an advertising message? The answer may depend on both the length of the ad and how often it is repeated. An experiment investigated this question using undergraduate students. All students viewed a 40-minute television program that included ads for a new smartphone. Some subjects saw a 30-second commercial; others, a 90-second commercial. The same commercial was shown either one, three, or five times during the program. After viewing, all the students answered questions about their recall of the ad, their attitude toward the smartphone, and their intention to purchase it. In this experiment, the length of the commercial and the number of times it was shown are
(a) the responses.
(b) the blocking variables.
(c) lurking variables.
(d) the explanatory variables.
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6.5 Effects of TV advertising. Which of the following is an important weakness of the experiment described in Exercise 6.4?
(a) This was not a matched pairs design.
(b) Because undergraduate students were used as subjects and knew what was going on, the results may not generalize to everyday television viewers.
(c) This was not a double-blind experiment.
(d) This experiment did not use a placebo.
6.6 Reducing smoking. The Community Intervention Trial for Smoking Cessation asked whether a community-wide advertising campaign would reduce smoking. The researchers located 11 pairs of communities, with each pair similar in location, size, economic status, and so on. One community in each pair was chosen at random to participate in the advertising campaign and the other was not. This is
(a) an observational study.
(b) a matched pairs experiment.
(c) a completely randomized experiment.
(d) a randomized block design.
6.7 Wine and heart health. To explore the effects of red wine on heart health, you recruit 100 volunteers. Half are to drink one glass of red wine a day with dinner for a month. The other half are to abstain from any alcohol for a month. The diets of all volunteers are otherwise the same. Women and men may respond differently to wine. Forty of the volunteers are women and 60 are men, so the researchers separately randomly assign half the women to the wine group and half the men to the wine group. The remaining volunteers are assigned to the no alcohol group. This is an example of
(a) a completely randomized design.
(b) a matched pairs design.
(c) a block design.
(d) an observational study.