PrepTest 155

This answer choice gestures toward describing the causation flaw, but subtly misdescribes the argument. The answer choice claims there was an "observed change," when one of the big problems with the argument is that no change was observed. Remember, there was just a single survey about the present-day passage rate — we don't have any observations that the passage rate changed over time.

This answer choice refers to the absence of evidence flaw. It occurs when an argument treats someone's failure to prove a claim as conclusive proof that the claim is false. In this argument, such a flaw might look like, "The Technology Institute has repeatedly failed to provide evidence that their new curriculum is improving the quality of the school's instruction. So we must conclude that the new curriculum has lowered the quality of the school's instruction." This is not what this argument is doing. This argument doesn't use a lack of evidence to draw its conclusion. Instead, it uses a survey of last year's students. So this answer choice misdescribes the premises of this argument, and is incorrect.

Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
The Technology Institute has been using an experimental curriculum for plumbers for several years. Last year, a survey found that only one-third of the institute's graduates could pass the plumbers' certification test, well below the national average. So, the new curriculum must have made plumbing instruction worse.

Strategy Overview:

1. Argument or facts? Always argument, so identify premises and conclusions of argument
2. Anticipate why the premises are not enough to prove that the conclusion is true. 
   1. Checking to see if a common logical fallacy is committed is very helpful.
3. Use anticipations to select the answer choice that:
4. Accurately describes the reason why the premises are not enough to prove that the conclusion is true

Answer Anticipation:
On an Errors in Reasoning question, we should take the time to articulate why the premise or premises aren't enough to prove that the conclusion is true. To help organize our thought process, we can think about the common flaws that arguments commit over and over again.

Experienced LSATers will immediately think of a causation flaw when the conclusion makes a causal claim. This conclusion is causal (the strong, active verb "lowered" indicates that this conclusion is causal). And the premises only show that there's a correlation between the implementation of the new curriculum and the graduates' low passage rate. But that doesn't mean the experimental plumbing curriculum caused the passage rate to ... go down the tubes (apologies). There could be several other reasons the passage rate is so low, especially because the correlation is pretty weak, too — the new curriculum existed at the school for several years before last year's survey.

But there's another issue here that observant test-takers might catch: the premises use an absolute number (one-third of graduates passed) as evidence that the quality has changed. We can't use a single, fixed number to show that something has changed. To conclude the quality of the plumbing program lowered, we'd need to know the passage rate before they implemented the new curriculum. Maybe this school has always been bad? Maybe it used to be even worse! Using absolute numbers to support a conclusion about a change is a common type of equivocation flaw on this exam.

A correct answer choice might describe either of these fatal flaws in the argument.

Answer Choice Explanation:
This accurately describes the equivocation flaw in this argument. The premises suggest that the instruction at the Technology Institute is below average — the survey indicates that graduates' passage rate is "well below the national average." And the argument does fallaciously use that evidence to claim that the quality of instruction has "diminished" — the conclusion claims that the new curriculum has "lowered the quality of plumbing instruction." Therefore, this answer choice is correct.

Key Takeaway:
The difference between relative and non-relative statements is a favorite topic on the LSAT, and it shows up all over Logical Reasoning, especially on Errors in Reasoning questions. We can't use non-relative claims (which state an absolute, static facts) to justify a relative conclusion (which are about to a comparisons or changes). We can't conclude that X is better than Y just because X is good, and we can't conclude that X has gotten better just because X is good right now.

This does not describe an error in reasoning. Referencing the average passage rate, in this case, does not require the speaker to give the exact figure for the average pass rate. The pass rate is just used as a benchmark to show the Technology Institute is currently providing below-average instruction. The author only needs to define the national average if the conclusion requires us to know the exact figure. For example, suppose this argument was, "Only one-third of the Technology Institute's plumbing graduates—well below the national average—were able to pass the plumbing certification test. This shows that at least one-third of Technology Institute's plumbing graduates would have been better off going to an average plumbing program." In that case, we'd need to know the average pass rate was two-thirds of plumbing program graduates.

This is a description of a sufficient/necessary fallacy, and there are no sufficient or necessary conditions mentioned in this argument, so that can't be right. This is a causal conclusion, not a conditional one.