LR Question 9 Explanation
QUESTION TEXT: In a recent field study of prairie plants, the more…
QUESTION TYPE: Flawed Reasoning
CONCLUSION: Having more plant species leads to better plant growth and better soil conditions.
REASONING: There is a correlation between more plant species and improved plant growth/soil conditions.
ANALYSIS: This argument makes a classic LSAT flaw. It confused correlation and causation.
We can’t say that one thing causes another just because the two things happen together. It could easily be the other way around. Maybe better soil conditions lead to a greater variety of plant species.
___________
- CORRECT. This matches. This is a more specific form of saying “mistakes correlation for causation”. And this particular reversal matches the situation in the stimulus: it’s quite possible that better soil leads to more plant species, rather than the reverse.
- Assuming “productivity” refers to plant growth, the argument does specify the mechanism: greater species variety. That counts as a mechanism. Mechanism just means the way something happens. You don’t need to get more specific.
- This isn’t taken for granted. The study was a field study of prairie plants. It sounds broad enough to cover prairie plants in general.
- This didn’t happen.
Example of flaw: I looked at two prairie plants growing in my backyard. This lets me make conclusions about all prairie plants in North America. - This is a different flaw. It’s common on the LSAT, but it doesn’t happen here. Here’s an example: Increase in number = 10 more, increase in proportion = 10% more. They’re pretty obviously different: 10% of America, for example is around 33 million people, which is a lot more than 10 people.
More Resources for Flaw Questions
- Flaw drills: Use these to practice making examples of abstract flaws.
- Intro Course lesson: This intro course lesson covers Flaw questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers flaw questions.
Graeme,
This was a classic flaw question that I got wrong because I second guessed myself. However, I have a bit of a hang-up with the correct answer choice that I hope you can clarify. I initially picked “A”, but second-guessed myself and switched my answer to “D”. The reason I did this was because of the words “the more vigorously the plants grew” in the stimulus. Now, I could easily see how one could mistake the correlation/causation of the amount of plant species with the soil quality. If it were just those two conditions, I would have stuck with “A”. However, it seems like the addition of “the more vigorously the plants grew” makes it hard for the correlation/causation to be mistakenly reversed. I didn’t understand how the plants vigorously growing could have led to more plant species in a plot. In your explanation, you only consider the soil quality and amount of species when discussing the mistaken causal relationship. Was the plants growing vigorously aspect simply meant to be ignored? I then picked “D” because it seemed like you couldn’t properly infer such a sweeping conclusion about all prairies from one field study.
Thanks in advance.
Great question. First, I think you could choose A just based on soil. A reversal doesn’t have to address every single aspect.
But second, vigorous growth could simply be the consequence of the soil, and more species are also a consequence of the soil. There’s also a third possibility: maybe weather conditions are better in this area, leading to vigorous growth. And because plants grow vigorously, more plants survive.
I agree it’s hard to go directly from vigor to more species, but we don’t need to. We can either look at soil, or bring in the support of another factor which leads to vigor.
Note: This is an old comment but I wanted to clarify the point.