Logical reasoning PrepTest 144 · Section 2 · Question 21

Incorrect. This argument doesn't jump from a part to a whole. Instead, this argument jumps from a statement that something isn't always a cause to a statement that it probably wasn't the cause in one case.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Flawed Parallel Reasoning

Stimulus Summary:
Despite humans bringing diseases with them about the same time as a bunch of extinctions, there were too many species for a single disease to wipe out, so the diseases probably weren't the cause.

Answer Anticipation:
In Flawed Parallel Reasoning questions, it's important to identify the flawed logic. Other elements of the stimulus can show up in the correct answer, but only elements related to the flaw must show up.

Here, the argument reaches a conclusion that one thing didn't cause another, even though they're correlated. It would be easy to get wrapped up in finding similar language in the answer choice, but stating that a correlation doesn't prove causation isn't flawed logic—in fact, it's commonly something that we need to point out in correct answers! So despite the heavily causal nature of the topic in the stimulus, the flaw isn't related to it. We must look elsewhere.

The argument disregards the correlation in reaching a conclusion that one thing didn't cause another, so we need to identify what is used to support that conclusion. And here, it's that a lot of different species went extinct, and no single disease brought over by humans could have taken them all out. However, the stimulus even notes that humans brought over a number of diseases, so it's possible that all of them together had an effect that no individual disease could have had. This is very much a part (no individual disease could have wiped out 55 species) to whole (so the diseases weren't the cause of the extinction) flaw, so we should find an answer that matches it.

Answer Explanation:
This answer jumps from what is true of the parts—the two individuals—to what is true of the whole. It states that, since each individual can't fix all of the problems in the apartment, that the two working together can't fix all of the problems in the apartment. That's a match for an argument stating that since each individual disease can't wipe out all 55 species, all of the diseases working together can't wipe out those species.

Key Takeaway:
Flawed Parallel Reasoning questions are distinct from Parallel Reasoning questions in that only elements related to the flaw need to match up. As we saw here, there was a lot of discussion of causality not being inferable from a correlation in the stimulus, which is not a flaw and thus didn't need to be replicated in the correct answer.

Incorrect. This answer choice assumes that no one will go to a restaurant they don't like, not that what is true of the part is true of the whole—whether you look at the parts/whole as the restaurants or the individuals.

Incorrect. The issue in this argument is an overlapping sets/inferring from quantifiers issue. The conclusion is too strong based on the weaker premises!

Incorrect. Considering the conclusion is about "some people," it's unlikely this answer is jumping from a part to a whole. The flaw here is another issue with a jump from a weaker premise to a stronger conclusion—if only some people see their symptoms reduced from the vaccine, then it's possible that others don't and thus derive no benefit from it.