Logical reasoning PrepTest 144 · Section 2 · Question 9

Incorrect. This answer might explain why the fish population continued to decline at Highwater, but the conclusion isn't about Highwater—it's about Quapaw and the rebounding fish population. As such, this answer doesn't affect the conclusion.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Both lakes - Both suffering from a decline in fish populations 10 years ago
Quapaw - Fishing ban, fish population recovers
Highwater - No fishing ban, fish population continues to decline
Conclusion - The fishing ban is probably the cause of the population rebound

Answer Anticipation:
Weaken questions frequently feature correlation/causation flaws, so you should be actively looking for them in this question type. Here, the premises establish a timeline of things that coincide, which generally suggests a correlation; the conclusion that a fishing ban "is probably responsible" for an increase in fish population is causal. Therefore, this argument is committing a correlation/causation flaw—there may have been another factor at play at Quapaw Lake that didn't happen at Highwater Lake. That said, the fact that this situation does include a control group (Highwater Lake didn't have the supposed cause and didn't see the supposed effect) does make this a stronger correlation/causation argument than they usually are.

Since we're trying to Weaken this argument, we should look for an answer that falls into one of the common categories:

(1) Identify an alternative cause
(2) Bring up counterexamples (though we already have a control group, so while possible this type of answer is unlikely)
(3) Suggest the causality is reversed (though the timeline where the ban happened before the rebound rules this out)

Because this argument is also based on a comparison between Quapaw and Highwater Lakes, we also have to be open to an answer that establishes a relevant comparison between them. Since the argument relies on one difference explaining another, any other relevant difference between the lakes would provide an alternative explanation and thus could weaken this argument.

Answer Explanation:
If this is the case, then the fishing ban probably didn't have much to do with the rebounding fish population since the ban likely didn't change much. Since the argument attempts to explain a phenomenon by correlating a change with it, showing that that "change" didn't really change much of anything weakens that relationship.

Key Takeaway:
Strengthen/Weaken questions featuring comparisons have tricky anticipations. Sometimes, you weaken an argument that relies on differences with similarities; other times—as here—a relevant difference can weaken the relationship. It's less important that you have some matrix of anticipations ready to go and more important that you recognize this issue is common in the question type, you identify it when it shows up, and you think through whether relevant similarities or differences will have the impact on the argument the question stem asks about.

Incorrect. Without connecting lake size to population growth or decline, this answer doesn't provide a comparison that affects the argument.

Incorrect. Without tying this into a ban on fishing, it's impossible to know if these strengthen or weaken the argument.

Incorrect. By bringing up a similarity between the two lakes, this answer rules out a potential alternative explanation for the different changes to the fish populations (the alternative being that the number of species affects the ability of the overall population to increase or decrease). So, if anything, this answer strengthens the argument.