PrepTest 107
[lcid:3524] Prep Test 107 LSAT — Logical Reasoning — S1
Logical reasoning
Question prompt
Linda says that, as
Remaining source text redacted.
Why the credited answer is right
Credited answer: B
The notes below walk through why it fits the stem and how to eliminate the rest.
Argument or Facts
Argument
Valid or Flawed
Flawed
Question Type
Flawed Parallel Reasoning Questions
Stimulus Summary
Linda (Scientist): Scientist → ~Appreciate poetry
Scientist --most--> Logical
Therefore - Appreciate poetry --some-- ~Logical
Answer Anticipation
This argument starts with a claim made by someone who is a member of the group that’s about to be discussed. Her claim is something she knows, so we can treat it as true (if someone believes something, it could be false; if they know it, it’s true and they’re aware of it). And it’s a conditional (“No As are B” is A → ~B), so we can diagram it out. The following statement is a premise (“since”) that is a quantified statement - a most statement, so we need to ensure we get the direction right. From there, we get a conclusion (since it follows a since statement), which is a some quantified statement.
The first thing we should consider is whether the premises can be combined. A conditional can be combined with a most statement, as long as the sufficient condition of the conditional shows up in the most statement. That’s the case here. When the shared term is the first term of the most statement, the inference is a some inference (when it’s the second term of the most statement, the inference is a most statement).
So we could draw a valid inference here: ~Appreciate poetry --some-- Logical
However, the conclusion is the negation of that statement, so we’ve found our flaw. Let’s find an answer that has the same flawed pattern:
Group A member: A → ~B
A --most--> C
Therefore - B --some-- ~C
(Note that we don’t need the negations to match up with what terms are negated in the stimulus; we just need terms that show up once to “flip” negation states as the stimulus did. So if we got: A → B, A --most--> C; therefore, ~B --some-- ~C, that would also be correct because the B and C are negated from the first time they show up.)
Answer choices
-
ARalph says that, as Remaining source text redacted.
Why choice A is not credited
Two issues here. First, Ralph’s statement isn’t about a group to which he belongs (he’s a biologist, not a marsupial). Second, the conclusion doesn’t negate terms from the premises. -
BFranz says that, as Remaining source text redacted.
Why choice B matches the stem
Franz speaks to a group that he’s a member of, and the conclusion includes terms from the premises negated (though it does shift from adult to child - which is the same as ~adult!). So let’s diagram:
Franz (father): Father → ~Want children to eat candy at bedtime
Father --most--> Adults
Therefore - Want children to eat candy at bedtime --some-- ~Adult (aka Children)
That’s the same flawed pattern of reasoning, with a negation of the valid inference that can be drawn, so this is the correct answer. -
CYuri says that, as Remaining source text redacted.
Why choice C is not credited
First, Yuri isn’t speaking about a group to which he’s a member (he’s not a wine). Second, the first term in his most statement isn’t shared with the other premise. -
DXi says that, as Remaining source text redacted.
Why choice D is not credited
First, Xi isn't talking about a group of which she’s a member (she’s a photographer, not color film). Second, the first term in her most statement isn’t shared with the conditional, as it was in the stimulus. -
EBetty says that, as Remaining source text redacted.
Why choice E is not credited
You could diagram this one out, but it’d be faster if you noted that the premise is about honest people, and the conclusion is about honest people - no negation there!
What this tests
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