Sharpen your ability to identify confounding variables, question sampling methods, and recognize when a study's design limits the conclusions it can support.
Question 1 of 5
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Question 1
A study finds that adults who drink coffee tend to live longer than those who do not. However, the coffee drinkers in the study also exercise more frequently. Which of the following best describes the role of exercise in this study?
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A city government surveys homeowners about a proposed property tax increase and reports: "A majority of residents oppose the tax increase." What is the main flaw in this conclusion?
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A medical study randomly selects 500 adults from a city and then divides them into two groups: one group receives a new vitamin supplement and the other receives a placebo. Neither the participants nor the researchers know who receives which treatment. After 6 months, the supplement group shows improved energy levels. Which of the following is true about this study?
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A tutoring company reports that students in its program scored an average of 78 on a standardized test, while students not in the program scored an average of 75. The company claims its program is effective. What additional information would be most important to evaluate this claim?
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Researchers give all 60 participants in a study a new herbal supplement and find that 70% report feeling less stressed after four weeks. They conclude that the supplement reduces stress. What is the biggest flaw in this study?