Logical reasoning PrepTest 136 · Section 2 · Question 24

Incorrect. This answer has an OR as the sufficient condition, so it's not a match.

Incorrect. Close, but this answer introduces a few elements that aren't parallel. Mainly, there's a lot of what people fear/believe in this stimulus, which introduces another flaw (subjective vs. objective). The initial premise is also just what "[m]any people" believe.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Flawed Parallel Reasoning

Stimulus Summary:
Econ theories sound AND Successfully implemented program → Inflation rate would have decreased
not Inflation rate decreased
Therefore - not Econ theories sound

Answer Anticipation:
This stimulus has an uncommon framing for a conditional statement, but that first sentence introduces a sufficient condition by saying, "Had the . . . " That's the same as saying, "If the . . . ," so we can diagram this out.

Also, before moving on, we wanted to note how we represented the nonconditional premise. While the inflation rate increasing and not decreasing aren't the same—after all, the inflation rate could have stayed the same—the inflation rate increasing guarantees that the inflation rate didn't decrease. Since the term used in the conditional premise is that inflation decreased, we framed it that way to keep it standardized.

With the argument laid out as in our Summary, we can see that the argument isn't an illegal negation or reversal—the conclusion is the negation of a part of the sufficient condition. Therefore, the argument is relying on the contrapositive of the premise, so we should start by taking it:
not Inflation rate decreased → not Econ theories sound OR not Successfully implemented program

And with that done, we can see the flaw in the argument—the inflation rate not decreasing justifies a conclusion that the economic theories of the party are not sound or it wasn't able to successfully implement its program. In picking one of the two possible conclusions as the only conclusion, the argument messes up the conditional logic. (Note that if the necessary condition of the contrapositive were an AND statement, this would be valid.) Since that AND (sufficient)/OR (necessary) statement is a key part of the flaw, we can eliminate any answer that doesn't have it. For any answer that remains, we're looking for the one that follows this structure:
A AND B → C
not C
Therefore - not A

Answer Explanation:
This answer has the AND sufficient condition and a premise that negates the necessary condition, so we should diagram it out:
Succeeded in selling subsidiaries AND Purchase new patent → Stock price doublednot Stock price doubled
Therefore - not Succeeded in selling subsidiaries
Same structure, so this is the same flaw. It even has the same shift from the necessary condition to a related one that guarantees it's met: The stimulus went from decreasing to increasing; this answer went from doubling to not increasing.

Key Takeaway:
Identifying key elements of a Parallel Flaw Argument—features that are directly related to the flaw and thus have to show up in any correct answer—is a great way to make some eliminations without needing to dive in more deeply. And if you're confident in your identification of these key features, you can also eliminate answers that have key features you didn't identify, as if they're not present in the stimulus, the answer must be wrong.

Incorrect. This answer features an illegal reversal—the necessary condition of the conditional premise shows up as the nonconditional premise, not the negation of it as in the stimulus.

Incorrect. This has a conditional premise with an AND necessary condition, so it's not parallel.