PrepTest 134, Section 1, Question 4
Physician: In an experiment, 50 patients with chronic(57 more words not shown)
Which one of the following,(11 more words not shown)
- AA patient's merely(16 more words not shown)
- BMost physicians believe(11 more words not shown)
- CNo other experiments(16 more words not shown)
- DSome of the(27 more words not shown)
- EThere was wide(17 more words not shown)
Reading the argument
The magnet group felt better. Was the magnetic field what helped?
The result is interesting: most patients who received magnets reported less pain, while very few untreated patients did. But the two groups didn't differ only in exposure to magnetic fields. One group received a treatment and the attention involved in applying it; the other received nothing.
What if touching their backs helped? Perhaps applying the magnets involved contact that felt like a small massage. Then the treatment process could reduce pain even if the magnetic field did nothing. The sample is also small, and we aren't told how the patients were assigned to groups. Those details leave questions about the experiment, though we shouldn't assume it was badly conducted merely because the description is brief.
What we’re looking for
We're asked for the strongest counter to the physician's conclusion. I want a reason the improvement might come from something other than the magnetic fields. We can accept the patients' reports and still question what caused the change.
Working the answers
- ACorrect
Just knowing that a treatment has been applied can produce improvement. That gives us a specific alternative explanation: the magnet group knew they were receiving something intended to help, while the other group received no treatment. The difference in reported pain could reflect that expectation rather than an effect of magnetic fields. This is the placebo possibility. It doesn't prove magnets are useless; it shows why this experiment hasn't separated their physical effect from the effect of receiving treatment.
- B
More effective than magnets doesn't mean magnets are ineffective. Medication could provide much more relief while magnets still relieved some back pain. The physician's conclusion is limited to whether magnetic fields probably help at all, not whether they are the best treatment available.
- C
We are discussing back pain. A failure to demonstrate an effect elsewhere, such as the neck, wouldn't establish that magnets fail to help the back. Also, the absence of other experiments is not an experiment showing no effect. C doesn't explain away the result we have.
- D
Believing in the treatment beforehand doesn't by itself show that the experiment was biased or its result unreliable. These scientists helped design the experiment but didn't conduct it, and the answer identifies no defect their beliefs produced. We would need a connection between the belief and a problem with the evidence.
- E
Different patients having different causes of pain doesn't tell us that the magnet and untreated groups differed in a way that explains the result. The two groups might each include a similar mix of causes. We would need more information about that distribution or its effect on improvement before treating this variation as evidence against the physician.
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