In a recent field study of prairie plants, the more plant species a prairie plot had, the more vigorously the plants ...

Skylar on July 13, 2020

@AllyPauley3, happy to help!

The passage tells us that a study of prairie plants revealed that prairie plots with more plant species were also observed to have more vigorous rates of growth and better soil related nutrients. Therefore, the passage concludes that having more species improves the prairie's ability to support plant life.

We should immediately notice a red flag in this logic. The study only tells us that prairie plots with more species also have qualities (vigorous growth and better soil) that are more able to support plant life. How do we know that this is causation and not correlation? And how do we know that the increased presence of species is what causes the effect of the prairie's increased ability to support plant life as opposed to the other way around? We don't, which is exactly what answer choice (A) points out.

Answer choice (D), on the other hand, suggests that the argument is vulnerable to criticism because the data is likely to be unrepresentative. This is incorrect because we are given no reason to believe that the field study of prairie plants used a bad sample. More importantly though, the issue with the passage is not the reported observations from the study but instead the unsupported jump to a conclusion based on these observations.

Does that make sense? Please let us know if you have any other questions!