LR Question 25 Explanation
QUESTION TEXT: To test the claim that vitamin C is effective in treating acne…
QUESTION TYPE: Weaken
CONCLUSION: We can tentatively conclude that vitamin C has no real benefit in reducing acne severity.
REASONING: Scientists administered vitamin C to one group of subjects and a placebo to a control group. The group receiving vitamin C had less severe acne during the study. However, it was later discovered that half of each group knew which pill they were given. There was no difference between groups for the people who did not know.
ANALYSIS: Essentially, we learn that only people who knew which pill they got had a difference in the result. This may point to a placebo effect explanation for the difference – maybe people who knew they got vitamin C expected clearer skin, or people who knew they got the placebo expected no change.
It is important to note, however, that half of the study is still valid. Half of the participants did not know which pill they were getting. The results from this half are not good: there was no difference in acne severity between the groups. This is why the author draws the conclusion that vitamin C has no real benefit.
To weaken this argument, we have to discredit this half of the study. If there were another flaw in the methodology, it would throw these results into question and mean that maybe it’s early to conclude that vitamin C doesn’t help.
___________
- CORRECT. This tells us that vitamin C actually did do something. If the vitamin C group started off worse, but ended at the same place, then they must have shown more improvement.
- This doesn’t weaken the argument. In fact, it eliminates a possible flaw in the methodology, strengthening the argument.
- It doesn’t matter if the severity was less than the average, so long as the two groups start equal.
- This doesn’t weaken the argument unless we know that people on the vitamin C side didn’t also consume these foods.
- It doesn’t matter if the pill-aware people didn’t take their pills, since we’ve already tossed their data out. We need a flaw in the data from people who didn’t know.
Recap: The question begins with “To test the claim that vitamin C is effective in treating acne”. It is a Weaken question. Learn how to master LSAT Weaken questions on the LSAT Logical Reasoning question types page.
More Resources for Weaken Questions
- Intro Course lesson: This intro course lesson covers Weaken questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers weaken questions.
Man, I hate the wording “had a history of”. could be the case that these individuals had bad acne years ago but were similar to the control group at the outset of the experiment.
On a weaken question you’re not looking to decisively destroy the argument. You’re looking to weaken it. It’s in theory possible that everyone’s acne from the vitamin C group had already resolved before the study began.
But….how likely is that really? Odds are people who have a history of having a problem, as a group, will keep having that problem to some degree. So A shows that the vitamin C group started with a likely disadvantage. This makes their subsequent equal outcome more impressive.