Logical reasoning PrepTest 138 · Section 3 · Question 7

Incorrect. A process can't "replace" a method that isn't already in use.

Incorrect. This answer reflects something the argument already established—the Researcher notes that she looked at "sites plagued by airborne copper pollution."

Incorrect. The Researcher's proposed method isn't to look at the amount of lichen in an area, but rather to look at the pollution absorbed by the lichen. There doesn't need to be a relationship between lichen and pollution to be able to find lichen and analyze it.

Incorrect. The lichen being used to measure pollution would be growing in the wild, so there's no need to grow it in a lab.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:
Hypothesis - Lichens can provide a cheaper way to monitor air quality
Study - Copper levels in lichens were compared to mechanical monitoring devices and they were just as accurate as the best
Conclusion - Lichens can replace expensive monitoring devices

Answer Anticipation:
The conclusion of this argument is relatively extreme—lichen analysis can "effectively replace" current devices "without loss of information." In other words, we can completely replace our current system with lichen.

This conclusion is based on a study done by a Researcher—is it broad enough to allow for such a conclusion to be drawn? The study did show that lichen analysis can be used to measure copper pollution, but there are plenty of other pollutants. Maybe lichen analysis only works for monitoring copper levels. The argument assumes that proving lichen accurately measures copper pollution means that it can accurately measure all pollution, so let's find an answer that establishes that.

Answer Explanation:
This answer strengthens the argument by stating that what the argument establishes as true of copper pollution—that lichen analysis can accurately measure it—is true of all other air pollutants. This means that lichen analysis can replace mechanical devices for all pollution, not just copper pollution, strengthening the argument.

Key Takeaway:
Broad/strong conclusions need premises that are just as strong and broad as they are to fully support them. When you note that a conclusion has a wide scope or strong language, compare it to the premises to see if it's justifiable. Most of the time, it won't be! Here, in particular, the conclusion was very broad, but the premises/study only discussed a single example. That's a large mismatch in scope.