QUESTION TYPE: Weaken
CONCLUSION: Magnetic fields can reduce back pain.
REASONING: An experiment, with two groups: those with magnets on their backs and those without. Those with magnets felt less back pain.
ANALYSIS: There were two differences between the groups:
- The first group had magnets on their back.
- The first group knew they were being treated.
The second difference could be the cause. This is called the placebo effect. The body can heal itself if it believes it’s being healed. It’s a useful effect, but it’s also very frustrating for doctors who design medical experiments. The LSAT often mentions it.
- CORRECT. The experiment would have been better if the second group had devices that looked like magnets applied to their back.
Then the experiment would have isolated the magnetic fields’ effect.
- Who cares what doctors believe? The entire medical profession could be wrong. That’s happened before: doctors used to believe that hand washing before surgery was silly.
- So? The doctor only claimed that magnets helped the back. Other parts of the body don’t matter. The doctor only claimed magnets help the back. There could be thousands of other studies about how magnets help the back, even if no studies have been done on, say, foot pain.
- Scientists are allowed to have hypotheses (beliefs). That’s why we use experiments: to test beliefs. If the experiment is well designed, scientists’ beliefs don’t matter. Not having the original scientists involved is a sign that the experiment was well designed: their beliefs can’t bias the results.
- I’ll explain with an example: headaches happen for many different reasons. That doesn’t change the fact that Advil can help with most headaches. The cause of the sore back doesn’t necessarily affect whether magnets can help sore backs.
Free Logical Reasoning lesson
Get a free sample of the Logical Reasoning Mastery Seminar. Learn tips for solving LR questions