Chapter 2: Problem 40
Explain why some studies include both a control group and a placebo treatment. What additional comparisons are possible if both a control group and a placebo group are included?
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Chapter 2: Problem 40
Explain why some studies include both a control group and a placebo treatment. What additional comparisons are possible if both a control group and a placebo group are included?
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Whether or not to continue a Mardi Gras Parade through downtown San Luis Obispo, \(\mathrm{CA}\), is a hotly debated topic. The parade is popular with students and many residents, but some celebrations have led to complaints and a call to eliminate the parade. The local newspaper conducted online and telephone surveys of its readers and was surprised by the results. The survey web site received more than 400 responses, with more than \(60 \%\) favoring continuing the parade, while the telephone response line received more than 120 calls, with more than \(90 \%\) favoring banning the parade (San Luis Obispo Tribune, March 3, 2004). What factors may have contributed to these very different results?
The article "Americans are 'Getting the Wrong Idea' on Alcohol and Health" (Associated Press, April 19,2005 ) reported that observational studies in recent years that have concluded that moderate drinking is associated with a reduction in the risk of heart disease may be misleading. The article refers to a study conducted by the Centers for Disease Control and Prevention that showed that moderate drinkers, as a group, tended to be better educated, wealthier, and more active than nondrinkers. Explain why the existence of these potentially confounding factors prevent drawing the conclusion that moderate drinking is the cause of reduced risk of heart disease.
"Fruit Juice May Be Fueling Pudgy Preschoolers, Study Says" is the title of an article that appeared in the San Luis Obispo Tribune (February 27, 2005). This article describes a study that found that for 3 - and 4 -year-olds, drinking something sweet once or twice a day doubled the risk of being seriously overweight one year later. The authors of the study state Total energy may be a confounder if consumption of sweet drinks is a marker for other dietary factors associated with overweight ... (Pediatrics, November 2005 ) Give an example of a dietary factor that might be one of the potentially confounding variables the study authors are worried about.
Swedish researchers concluded that viewing and discussing art soothes the soul and helps relieve medical conditions such as high blood pressure and constipation (AFP International News Agency, October 14,2005 ). This conclusion was based on a study in which 20 elderly women gathered once a week to discuss different works of art. The study also included a control group of 20 elderly women who met once a week to discuss their hobbies and interests. At the end of 4 months, the art discussion group was found to have a more positive attitude, to have lower blood pressure, and to use fewer laxatives than the control group. a. Why would it be important to determine if the researchers assigned the women participating in the study at random to one of the two groups? b. Explain why you think that the researchers included a control group in this study.
The article "I'd Like to Buy a Vowel, Drivers Say" (USA Today, August 7,2001 ) speculates that young people prefer automobile names that consist of just numbers and/or letters that do not form a word (such as Hyundai's XG300, Mazda's 626 , and BMW's 325i). The article goes on to state that Hyundai had planned to identify the car now marketed as the XG300 with the name Concerto, until they determined that consumers hated it and that they thought XG300 sounded more "technical" and deserving of a higher price. Do the students at your school feel the same way? Describe how you would go about selecting a sample to answer this question.
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