PrepTest 101
[lcid:3501] Prep Test 101 LSAT — Logical Reasoning — S2
Logical reasoning
Question prompt
Altogether, the students in
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
Flawed
Question Type
Flawed Parallel Reasoning Questions
Stimulus Summary
Ms. T’s class collected the most aluminum cans, so the student who collected the most must be in her class.
Answer Anticipation
Knowing the common errors in reasoning is key to doing well on the LR section of the LSAT, and this is a great example of one of those common flaws.
Here, the premise compares Ms. T’s class to all other classes. From that, it draws a superlative conclusion about a specific student in her class. That’s jumping from something that’s true of a whole to saying it’s also true of a part of that whole - a classic Part vs. Whole flaw.
Here, it’s possible that Ms. T’s students each collected an above-average number of cans, but there was one superstar in another class that collected the most, while the rest of the students in that class collected none. In that case, the student who collected the most cans would not be in the class that collected the most cans.
Let’s find an answer that commits a similar Whole to Part flaw (the specific version of the flaw present here, since the premise is about the class/whole and the conclusion is about the student/part).
Answer choices
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AAltogether, more trees were Remaining source text redacted.
Why choice A is not credited
This argument is valid, and it also compares only three classes, not all classes. And it compares the total of those classes combined, not individually, as the stimulus did. -
BMore than half of Remaining source text redacted.
Why choice B is not credited
This argument makes an overlapping sets flaw - it assumes that there isn’t enough overlap between the two groups to mean some students fall outside of it. That’s a separate flaw. -
CMr. Rowe's Milton Elementary Remaining source text redacted.
Why choice C is not credited
This argument compares only two groups, and it doesn’t draw a superlative conclusion. This argument is flawed in that it assumes something about the relative cost of candy bars and raffle tickets, not that there’s a connection between a whole and the parts that make it up. -
DThe total number of Remaining source text redacted.
Why choice D matches the stem
If you replace “tickets to the school fair sold” with “aluminum cans collected,” this argument is exactly the same as the one in the stimulus, going from what is true of a whole (Ms. R’s class selling the most tickets) to a part of that whole (the student who sold the most tickets). This answer is therefore correct. -
EMs. Ventura's Milton Elementary Remaining source text redacted.
Why choice E is not credited
The conclusion of this argument is about the average, not a single student, so it doesn’t commit a Part vs. Whole flaw. In fact, this argument is valid, as fewer students making more birdhouses must have, on average, made more birdhouses per student than the other classes.
What this tests
Discussion
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