Logical reasoning PrepTest 134 · Section 1 · Question 4

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Study - 50 back pain sufferers
Group 1 - Magnets and back pain relief
Group 2 - Nothing and no back pain relief
Conclusion - Magnets help back pain

Answer Anticipation:
Whenever there's a study, you should always consider a sampling flaw, and a correlation/causation flaw.

For the sampling flaw, 50 is a bit on the low side, but the conclusion is only that magnets can relieve "some" back pain, so you only need a few examples for that to hold. The groups weren't randomly assigned, which could be attacked in a correct answer.

For the correlation/causation flaw, the argument does jump from a correlation between magnets and back pain relief to a conclusion about magnets relieving back pain. That's a classic correlation/causation flaw, so we can weaken it by:
(1) Identifying an alternative cause of back pain relief—This would overlap with the sampling flaw in highlighting something that was true of Group 1 but not Group 2 that could have led to it
(2) Counterexamples - This, however, is less likely since the conclusion is that magnets relieve "some" back pain, so finding people with back pain that isn't relieved with magnets aligns with the conclusion
(3) Reversed causality - This doesn't make much sense since the magnets were applied before the back pain relief happened.

Answer Explanation:
This answer brings up a potential alternative cause of the back pain relief—the placebo effect. Since the first group could physically feel the magnets, and the second group was aware they weren't getting treatment, it could have been that placebo effect making the first group feel better.

Key Takeaway:
The placebo effect is a common alternative cause brought up in experiment-based medical questions. It serves as an explanation outside of the cause that is likely reached in the conclusion.

Incorrect. The conclusion states magnets are effective at relieving back pain, so it doesn't affect the argument if something else is more effective.

Incorrect. Other areas are out of scope of the argument about back pain—there may be something unique about that area that lends itself to magnetic cures.

Incorrect. Scientists believing something is true doesn't invalidate a study into the truth of it unless that belief influences the study. There's no indication that that was the case here, especially since these scientists weren't involved in conducting the experiment. Biases held by scientists are much more likely to affect outcomes when they're the ones making observations or analyzing the data.

Incorrect. The causes of the back pain are out of scope—it's the cause of the relief that's relevant.