Logical reasoning PrepTest 129 · Section 1 · Question 17

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Flawed Parallel Reasoning

Stimulus Summary:
Warm air tends to increase humidity
As humidity goes up, rainfall tends to go up
Rainfall has been going up for most continents
Therefore - Temperature has likely gone up

Answer Anticipation:
This argument brings up some positive correlations that chain together. It then reverses that relationship in drawing the conclusion.

But that's a problem because correlations aren't reversible. Sure, it might be rainy most of the time the air is warm, but that doesn't mean that the air is warm most of the time it's rainy. To see why, think about this statement: Most of the time we watch the news, it's on TV. This doesn't mean that most of the time we watch TV, we watch the news!

So let's find an argument that similarly chains these positive correlations together, and then it establishes that the end of the chain happened and concludes that there is strong evidence the beginning of the chain also happened.

If we want a bit of structure to use here, with keywords included:
A tends to be B
The more B, the more C
C has been going up
Therefore, A must be going up

Answer Explanation:
Fresh food tends to be nutritious
The more nutritious, the healthier one is
Health has been going up
Therefore, food freshness must be going up
This is the exact same structure and therefore the same flawed logic as the stimulus, so this is the correct answer.

Key Takeaway:
You can use notation similar to conditional logic to map out any argument that has repeated terms that determine the structure of the argument. Identify the key ways that terms are linked together (e.g., "tends to", "the more . . . the more . . . "), and then substitute letters in for the overlapping elements. This can be an easy way to work through a question that might otherwise be a bit complicated!

Incorrect. This answer opens with its conclusion (since it's followed by "for"), but there's no increase noted there, so we can safely rule this out.

Incorrect. The conclusion here brings in a new term—automobile travel—whereas the stimulus doesn't, so this answer has a different flaw.

Incorrect. The statistics here don't note a tendency of one thing to be another, just two things that are currently true. Additionally, the conclusion here is that two elements are not essential, which is a completely different type of argument than the stimulus.

Incorrect. The first and second premises here do match up individually with the statements in the stimulus, but they don't chain together as the ones there do, so this answer isn't parallel.