PrepTest 104

[lcid:3512] Prep Test 104 LSAT — Logical Reasoning — S1 Logical reasoning

Question prompt

Researcher: The vast majority Remaining source text redacted.
Why the credited answer is right

Credited answer: D

The notes below walk through why it fits the stem and how to eliminate the rest.

Argument or Facts

Argument

Valid or Flawed

Valid

Question Type

Parallel Reasoning Questions

Stimulus Summary

Most dreams don’t come true, so it’s unreasonable to believe your dreams predict the future if some of them do.

Answer Anticipation

Quantifiers/logical force keywords are key in Parallel Reasoning questions, and this argument is very strongly based on them. It also has a key concept in the conclusion that we should focus on as we work through it!
The premise here talks about the “vast majority” of dreams not being predictive, so we’re looking for an answer with a “most” premise. (Yes, “vast majority” sounds like more than most, but the LSAT really only cares about three levels - possibility (some), probability (most), and certainty (all/none), so we collapse anything over 50% but under 100% to most). From that, it has a conclusion based on some (“several”) dreams being predictive (the flipside of the most premise) not reasonably leading to a conclusion. The judgment that an argument is unreasonable will likely be mirrored in the correct answer, as reaching a judgment on an argument is a key feature on the LSAT!
So let’s find an answer where it jumps from a premise about most of something not having a feature meaning that even if some of it does have the feature, it’s unreasonable to conclude that the feature is generally present.

Answer choices

  1. A
    It is unreasonable to Remaining source text redacted.
    Why choice A is not credited
    This answer has all the relevant parts (a most premise; a some conclusion about a conclusion being unreasonable). It would survive on the first pass, but when we ended up with two answers that check those boxes, we’d dig in more and see that this answer isn’t parallel. The premise is about most new drugs, whereas the conclusion is about some patients. In the stimulus, the premise was about most dreams (not being predictive), and the conclusion was about some dreams (being predictive) - there’s no shift in what the quantifiers apply to.

  2. B
    Many people who undergo Remaining source text redacted.
    Why choice B is not credited
    The premise here is about “[m]any” people, which is a some quantifier, not a most quantifier. (This can be a hard one, but it’s true that many people are Americans, even though there are only about 330m in a world of billions.)

  3. C
    Even though many cancer Remaining source text redacted.
    Why choice C is not credited
    This argument lacks a most premise, so we can eliminate it.

  4. D
    A number of people Remaining source text redacted.
    Why choice D matches the stem
    This argument has all the parts we identified as being relevant, so it would survive the first pass and end up being compared to (A) and the stimulus to figure out which one is right. Here, the quantifiers line up - the most is about people taking aspirin (not dying prematurely), and the some is about people taking aspirin (dying prematurely). That’s the same group, and the connected term is negated in them, which lines up with the stimulus. From that, it concludes that reaching a certain conclusion is unreasonable, lining up with the stimulus.

  5. E
    A significant number of Remaining source text redacted.
    Why choice E is not credited
    This answer also lacks a most premise (“A significant number” of children with cancer could be 5% - that’s still a significant number, even if it’s not a majority), so we can eliminate it.

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