PrepTest 154

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Flawed Parallel Reasoning

Stimulus Summary:
Wei didn't get their cars' transmissions serviced for 12 years and didn't experience any transmission problems. Therefore, it must not be true that most cars will develop transmission problems if their transmissions aren't serviced at least once every three years.

Answer Anticipation:
Wei is saving some money on their two cars, but anecdotal evidence about two cars can't disprove a rule that only needs to be true of MOST cars (more than half of cars) to be correct. Even if only 51% of cars develop transmission problems if not serviced every three years, the "most" rule is still valid. Wei's two cars could just be among the 49% that won't develop problems. This is a fallacy of quantification; SOME (at least one) evidence isn't strong enough to disprove a MOST (more than half) rule.

Since this is a parallel flaw question, we're anticipating a correct answer choice that also expresses an attempt to disprove a MOST-quantified rule by presenting SOME-quantified evidence.

Answer Explanation:
"The vet says MOST cats develop dental problems if their teeth don't get cleaned annually, but SOME cats (including my one cat) do not, so the rule must not be true." Just like in the stimulus, this is an attempt to prove a MOST rule false by introducing evidence with a quantification of "SOME."

Key Takeaway:
Pay close attention to quantifier words like "MOST" "SOME" and "ALL." When they appear in arguments you know from the question type to be flawed, always look for fallacies of quantification.

Incorrect. This is the wrong fallacy. B expresses an ad hominem. The equivalent for this argument would be "but the people who make this claim all sell transmission service, so the claim must be false, since they stand to profit from people believing it."

Incorrect. The speaker is wrongly assuming that "Driving fast increases the chance of an accident" means "ONLY those who drive fast increase their chance of an accident," in other words, the fallacy of the converse. There's still a misapplication of logical force here, but it doesn't match the form of the fallacy found in the stimulus.

Incorrect. This isn't an issue with quantification, it's an issue with categorization. The speaker has provided no evidence they bought "a good pair of boots." In fact, their on-sale, discount boots are probably not a good pair, so they aren't in the group the rule about good boots applies to. Definitely a fallacious argument, but not an attempt to disprove MOST with SOME.

Incorrect. This is a temporal fallacy. What's happened in the past will not necessarily continue to happen. The area could have a drought. We're looking for a fallacy of quantification, so this isn't the right answer.