Unplugged Practice Test: Logical Reasoning Set 3, Question 21 (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
Most certified weld inspectors hold that visible spatter around a seam is a sign of careless work. These inspectors are mistaken. The one thing behind their view is that spatter appears on such a large share of seams that a spatter-free seam stands out to anyone who examines welds all day. Their thinking runs like that of a driver who, after 15 years on a single gravel route, concludes that gravel roads are by their nature unsafe.
21. The reasoning in the argument is flawed in that the argument
- (A)offers no support for its position beyond the say-so of people presumed to be experts
- (B)counts an account of how people came to hold a view as enough to show it false
- (C)sets aside a claim on the ground that those who make it have something to gain by making it
- (D)mistakes something required for a weld's being sound for something that by itself makes it sound
- (E)treats what is enough to make workmanship poor as also being needed to make it poor
BWhy (B) is correct
The argument says most certified weld inspectors are mistaken that visible spatter marks careless work, and its whole reason is that spatter appears on so large a share of seams that a spatter-free seam stands out to anyone who examines welds all day, the same shape as a driver who, after 15 years on a single gravel route, concludes gravel roads are by their nature unsafe. Explaining why the inspectors hold their view, familiarity with spatter, never shows the view is wrong. That's the move (B) names: an account of how a belief formed gets treated as enough to prove it false.
Why the other answers are wrong
AWhy (A) is wrong
(A) isn't the issue, since the argument isn't leaning on the inspectors' authority, it's rejecting their judgment.
CWhy (C) is wrong
(C) doesn't fit either, since the argument never claims the inspectors gain something by holding their view.
DWhy (D) is wrong
(D) describes confusing something required for a sound weld with something that alone makes it sound, which isn't the move here.
EWhy (E) is wrong
(E) describes the reverse confusion, treating what's enough for poor workmanship as also needed for it, which also isn't what this argument does.
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.
