Logical ReasoningDifficulty: Hard

PT155 S1 Q17 ExplanationFor several years the Technology Institute

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsFlaw

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Stimulus

For several years the Technology Institute has used a new experimental curriculum in its plumbing program. A survey last year found that only one-third of the Institute's plumbing graduates—well below the national average—were able to pass the plumber's certification has lowered the quality of plumbing instruction.

What this question is testing

Flaw

Your task

Describe the reasoning error the argument actually commits.

Common trap

Answers that name a real logical flaw the argument doesn't actually make.

Winning move

Articulate the gap in the reasoning yourself, then match it to the choice that describes that gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
17.

The reasoning in the argument is most vulnerable to criticism on the grounds

Answer choices, explained

  1. Not Causal25% picked this

    treats a phenomenon as an effect of an observed change in the face of evidence indicating that it may be

    This answer refers to the famous Causal flaw, in which an author overconfidently concludes one possible causal explanation where others might exist (specifically, this answer is saying, "You're assuming that Y is an effect of X when it really might be that Y causes X, i.e. Reverse Causality"). We didn't have any correlation here that could be vulnerable to alternate explanations of Reverse Causality. We know the chronological sequence. The new curriculum has been used. Later, once people graduated from that course, their pass rate was 33%. The author does think that the new curriculum caused that 33% pass rate, but we would sound crazy trying to argue, "Hey, author --- did you ever consider that maybe that 33% pass rate caused the new curriculum?" because we know that the 33% didn't happen until after the new curriculum was already built and taught.

  2. Trap7% picked this

    uses a lack of evidence that the quality of the Institute's plumbing instruction has increased as though it were conclusive

    Not Unproven vs. Proven False Bad Evidence Match This refers to another of the ten famous flaws, Unproven vs. Proven False, in which an author explains how someone failed to prove X (either through faulty reasoning or through lack of evidence) and then concludes illicitly that X must be false. This argument doesn't have that sort of evidence. The conclusion does indeed conclude that quality has decreased, but the evidence wasn't the author saying, "No one's been able to prove that quality has increased!" The evidence was, "The pass rate sucks. It's well below the national average."

  3. Correct56% picked this

    concludes that something has diminished in quality from evidence indicating that it is

    Why this is right

    If a Flaw answer describes a 2-part reasoning move, like confuses X with Y mistakes Y for X concludes Y on the grounds that X infers, from the claim that X, that Y then we want to ask ourselves whether the Evidence part and the Conclusion part match up with their respective targets. Did this argument conclude that "something has diminished in quality"? Sure, the conclusion is saying that quality of plumbing instruction has diminished in quality. Did the evidence establish that the quality of plumbing instruction is "of below-average quality"? Yes, basically. It established that certification test scores are of below average quality (they are well below the national average). To accept this answer, we have to sort of accept the idea that ability to pass this test is some indication of quality of instruction. That might make us hold off on picking this on the first pass, but it's a pretty common sense assumption to think that a plumbing program's main goal with its instruction is to get you certified as a plumber. So the less it succeeds in getting students certified, the lower quality it was.

    Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.

  4. Never a Flaw (specify number)2% picked this

    uses a national average as a standard without specifying what that

    There are hundreds of trap answers written in this style, in which the complaint is that we didn't name names, we didn't provide exact definitions / numbers / measurements. These questions aren't hinging on specific facts, just the logical force of ideas. Being "below-average" has some logical force, regardless of what specific number that average is.

  5. Trap9% picked this

    confuses a factor’s presence being required to produce a phenomenon with the factor’s presence being sufficient in itself

    Not Necessary vs. Sufficient Out of Scope: required to produce phenom This refers to the #1 famous flaw, Necessary vs. Sufficient, in which the author presents a conditional logic rule and then makes an argument that interprets that rule in an illegal backwards or negated fashion. We can start by asking ourselves, "Was there a conditional logic rule in the premise?" There was not, here, so this answer has no chance. Nothing in the argument talks about something being required to produce a phenomenon.

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