Do antioxidants prevent cancer? People who eat lots of fruits and vegetableshave lower

Chapter 0, Problem 9.45

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Do antioxidants prevent cancer? People who eat lots of fruits and vegetableshave lower rates of colon cancer than those who eat little of these foods. Fruitsand vegetables are rich in antioxidants such as vitamins A, C, and E. Willtaking antioxidants help prevent colon cancer? A medical experiment studiedthis question with 864 people who were at risk of colon cancer. The subjects weredivided into four groups: daily beta-carotene, daily vitamins C and E, all threevitamins every day, or daily placebo. After four years, the researchers weresurprised to find no significant difference in colon cancer among the groups.14(a) What are the explanatory and response variables in this experiment?(b) Outline the design of the experiment. Use your judgment in choosing thegroup sizes.(c) The study was double-blind. What does this mean?(d) What does no significant difference mean in describing the outcome of thestudy?(e) Suggest some lurking variables that could explain why people who eat lots offruits and vegetables have lower rates of colon cancer. The experiment suggests that these variables, rather than the antioxidants, may be responsible for theobserved benefits of fruits and vegetables.