Unplugged Practice Test: Logical Reasoning Set 1, Question 20 (Flaw)
Taking the test? Finish it first. This page shows the answer.
- Flaw questions ask you to name the reasoning error the argument commits, not to judge whether its conclusion is true.
- Before you read the choices, describe the argument's error in your own words. Most Flaw questions reward 1 of a small set of recurring patterns, so naming the pattern first keeps the trap answers from sounding right.
- Every question on this test is original, written to the same logical skeletons as real questions, and Steve checked every one himself before release.
The question
Auditor: Warehouses that switch to a night-only picking schedule are very likely to record a steep rise in mispacked orders. The Calder Street warehouse has recorded a steep rise in mispacked orders. So the Calder Street warehouse very likely switched to a night-only picking schedule.
20. Which one of the following most accurately describes a flaw in the reasoning of the auditor's argument?
- (A)It ignores the chance that one item in a category is atypical of that category in ways that matter here.
- (B)It runs together the claim that two things are regularly found together with the claim that one of them always brings about the other.
- (C)It moves from the likelihood that things of one sort have a given property to the likelihood that something with that property is of that sort.
- (D)It handles a circumstance that would suffice to make its conclusion true as one the conclusion could not hold without.
- (E)It sets aside a claim by faulting the person who advances it instead of weighing the claim on its own merits.
CWhy (C) is correct
The premise says warehouses that switch to a night-only picking schedule are very likely to see mispacked orders spike, and Calder Street's mispacked orders did spike. The auditor concludes Calder Street very likely made that switch. But knowing that night-only warehouses tend to have this property doesn't mean that a warehouse with this property is very likely night-only; the argument runs the likelihood in the wrong direction.
Why the other answers are wrong
AWhy (A) is wrong
(A) Nothing here turns on Calder Street being an unusual case within some category; the problem is the direction of the inference, not whether Calder Street is typical.
BWhy (B) is wrong
(B) The argument doesn't confuse two things merely being correlated with one causing the other; it reverses a probability, it doesn't claim causation.
DWhy (D) is wrong
(D) There's no mix-up between a condition that guarantees the conclusion and one the conclusion can't do without; the flaw is the backward likelihood, not a sufficiency-necessity slip.
EWhy (E) is wrong
(E) The auditor isn't dismissing anyone's claim by attacking the person who made it; there's no person being argued against here at all.
Common questions
What type of question is this?
Flaw. Flaw questions ask you to name the reasoning error the argument commits, not to judge whether its conclusion is true.
How do I get better at Flaw questions?
Before you read the choices, describe the argument's error in your own words. Most Flaw questions reward 1 of a small set of recurring patterns, so naming the pattern first keeps the trap answers from sounding right. The free LSAT cheat sheet lists the wrong-answer patterns to watch for on every type.
