PrepTest 132

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Critic – Astronauts are unlikely to survive a trip to mars, so it would be wrong to send them.
Rebuttal – Each stage of the trip is quite safe, so the entire trip is therefore quite safe.

Answer Anticipation:
The premises here are about "every stage" of the trip, and the conclusion is about the trip as a whole. That sure seems like a jump from what's true about the parts of something to what's true of the whole thing (see the preceding question in this section for an example of the reverse).

Even if each stage of the trip is pretty safe, that small amount of danger at each step may, over time, add up to quite a dangerous trip! Imagine, say, that there's a 1% chance of fatal catastrophe at each stage. If there are several hundred stages, those astronauts are almost certainly not making it back alive.

The correct answer should highlight that just because something is true of each of the parts of something doesn't mean it'll be true of the whole.

Answer Explanation:
It's quite unlikely that each stage will have a fatal catastrophe, so it's quite unlikely that the trip will have a fatal catastrophe. That infers something true of each part is true of the whole, so this is the correct answer.

Key Takeaway:
While a part-to-whole/whole-to-part flaw can sometimes be more obvious in talking about a collection, or society, or a team, the whole can sometimes be more subtle—like here, where it talks about a trip and stages. However, any time you see an argument that splits something up, you should start thinking about a part/whole flaw.

Incorrect. The conclusion is that the risk to the astronauts is "exaggerated," which doesn't necessarily mean that a fatal catastrophe can't occur.

Incorrect. Similar to (B), the argument doesn't conclude that the trip is safe, but rather that the risk is exaggerated.

Incorrect. Yet another answer that highlights a jump from possibility to certainty, when the stimulus always deals in probability.

Incorrect. This answer is the absence of evidence flaw answer. However, the author of this argument doesn't point out a flaw in the opposing argument; she points out information that she believes shows the opposing point is wrong. When the author of a rebuttal offers her own evidence to prove the opposite conclusion instead of just highlighting a shortcoming in the opposing point, the argument doesn't commit an absence of evidence flaw.