Logical Reasoning

PT139 · S4 · Q11 Plumb-Ace advertises

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

  • Save & drill this skill — build targeted practice sets from questions like this one

  • Video walkthroughs — watch every question solved step by step

  • 81 official LSATs — as questions, timed sections & full-length tests

Start practicing free

Plumb-Ace advertises that its plumbers are more qualified than plumbers at any other major plumbing firm in the region because Plumb-Ace plumbers must complete a very difficult certification process.

Conclusion (clearly)

The certification process at Plumb-Ace is not very difficult.

Evidence (because)

Nearly everyone who takes the written portion of the certification exam passes it very easily.

Evaluate

Given that ... nearly everyone who takes the written portion passes it, How could we still argue that ... the certification process is very difficult?

For me, this took me back to being 16 again. The written portion of the driver's license test wasn't scary. Almost everyone I knew passed that with little prep. But the driving portion of the driver's license test was famous for flunking people. You had to master 3-point turns, parallel parking, checking blind spots, hands at 10 & 2, etc.

Similarly, maybe it's easy to pass the written portion of this plumbing certification but it's really hard to pass other portions of the test (like where you have to rebuild a toilet from scratch).

This argument seems to resemble one of our top 10 famous flaws, Part vs. Whole. The argument is thinking that because PART of the process is not very difficult (almost everyone passes it very easily) it must be that the WHOLE process is not very difficult.

Goal

Let's look for an answer choice pointing out that other aspects of the test might be really hard to pass.

Or look for an answer describing this flawed move from Part to Whole.

11.

The reasoning in the argument is flawed in that it

  1. treats something that is necessary

    Not Necessary vs. Sufficient

    This describes the #1 famous flaw, Necessary vs. Sufficient, in which an author presents a conditional logic rule as one of his premises, but then applies that rule illegally in some reversed or negated fashion. There's no conditional logic premise here, so no chance this is correct. The only premise is "nearly everyone who takes the written portion passes it easily."

    14% picked this

  2. takes for granted that plumbers

    Too Strong: unless Not Assumed

    When a flaw answer starts with takes for granted / presumes / fails to establish, we can ask ourselves whether the author needed to assume the idea that follows. Did this author logically commit himself to believing this: If you haven't completed → then you are not some certification process qualified Definitely not. This doesn't reflect any reasoning move the author made. He made only one move: If the written portion of → then the overall some certification process is not process is not difficult difficult

    2% picked this

  3. overlooks the possibility that plumbers

    Irrelevant Objection Relative vs. Absolute

    When a flaw answer starts with fails to consider / overlooks the possibility, we can ask ourselves whether the idea that follows sounds like a weakening objection. Can we hurt the argument by saying, "Hey, author -- the certification at other plumbing agencies is even easier than at Plumb-Ace"? No. Establishing that other tests are even easier doesn't establish that this test is difficult. It only establishes that this test is more difficult. LSAT frequently tests this distinction between Relative and Absolute language. If I say, "This 2nd grade math test is hard. After all, the 1st grade math test is even easier", you would correctly say, "This 2nd grade math test is not hard. It's harder than a 1st grade test, but it's not hard."

    13% picked this

  4. infers that a claim is

    Trap

    Not Unproven vs. Proven False Bad Evidence Match This describes the famous flaw, Unproven vs. Proven False, in which an author concludes that someone's claim is wrong, merely because they unsuccessfully tried to prove it was true. Here, the author does infer that the claim "this certification process is very difficult" is false. Does his evidence describe the argument that Plumb-Ace makes in favor of claiming that it's very difficult? No. His evidence doesn't reference Plumb-Ace's argument for this claim at all. His evidence merely points to the very high passing rate for the written portion.

    7% picked this

  5. Correct

    presumes that since one part

    Why this is right

    This describes the famous Part vs. Whole flaw. Because this answer presents a two-part move (since X, Y), we want to ask ourselves whether we can match this to the argument. Did the author's evidence say that, one part of a whole lacks a certain characteristic? Yes. The written portion is a part of the whole certification process, and the author is showing that the this part lacks the characteristic of being "very difficult" (after all, almost everyone passes it very easily). Does the author's conclusion act like the whole must lack that characteristic as well? Yes. The conclusion is that the certification process overall clearly lacks the characteristic of being "very difficult".

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

    64% picked this

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

Save and practice this skill
LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free