Logical reasoning PrepTest 121 · Section 4 · Question 8

Incorrect. The argument has already established that age is one of the two most important factors in determining the value of a stamp, so this doesn't add much to the argument. It's also relative—the older, the more valuable—so we can't say that a "quite old" stamp is old enough to be "highly" valuable. Finally, the conclusion relies directly on the printing error to prove the conclusion (as shown by the conclusion being attached to it with "since"), and this answer doesn't bring that premise into the equation.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Sufficient Premise

Stimulus Summary:
Important stamp factors - Rarity, age, condition
This stamp - Quite old, "fine" condition, printing error
Conclusion - The stamp is probably valuable

Answer Anticipation:
The stimulus sets out the two most important criteria for determining the value of any stamp in good condition—rarity and age. It establishes that the stamp is in good condition ("find specimen"), and that it's "quite old." However, it doesn't directly establish the third criteria—the rarity of the stamp. Instead, it establishes that the stamp has a printing error.

Since that premise doesn't directly address any of the three criteria for value, and the other two criteria have already been established, the argument is relying on the printing error establishing that the stamp is rare. Therefore, we should look for an answer stating that.

Answer Explanation:
By definition, something that happens only "a few" times is rare. This answer thus establishes that this stamp with the printing error must be rare, and since it's also old and in good condition, it checks all the boxes that determine value. It therefore justifies the conclusion and is correct.

Key Takeaway:
The stimulus here gives you two huge hints that the rarity and the printing error are going to be linked in the correct answer. First, they're both mentioned only once in the stimulus, whereas the other key ideas are raised twice—once in the rule, and once in a premise that's meant to trigger the rule. Second, the statement about the printing error is directly tied to the conclusion as its support—it's in the same sentence and connected with "since."

Incorrect. This answer is trying to get you to think that this means the printing errors are rare. However, it establishes only that stamps with printing errors aren't out in the wild. It could be the case that such misprints are mass produced and are thus very common, but that collectors buy them up quickly. In this case, the misprinted stamps wouldn't be rare, they'd just be off the market. There's a difference between those two ideas!

Incorrect. If this answer is true, then it's particularly important to establish that a stamp is rare in order to determine that it's highly valuable. Since the argument hasn't established that this misprinted stamp is rare, this answer doesn't justify the conclusion.

Incorrect. This stamp is a "fine specimen," and the statement about value limits itself to discussing stamps in good condition, so stamps in poor condition and any rules about them (outside of a rule talking about only stamps in poor condition) are out of scope.