Which of the following, if true, would most weaken the argument that a new drug is effective because patients improved after taking it?
- A. The drug is expensive to manufacture
- B. A group given a placebo improved by the same amount
- C. The drug has been approved in other countries
- D. Some patients disliked the taste
Explanation
If untreated patients improved equally, the improvement cannot be attributed to the drug, which is precisely why controlled trials use a placebo group. Cost, taste and foreign approval say nothing about whether the drug works. A weakening statement must attack the link between the evidence and the conclusion.
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