Q10 - To prove that this Super XL

[mshinners]

Question Type:
ID the Flaw

Stimulus Breakdown:
After using your vacuum, I used my vacuum. My vacuum picked up dirt yours missed, so mine is better!

Answer Anticipation:
In order to truly compare these two vacuums, the test would have to be run in both orders to see which one picked up more first/second. It could be the case that no vacuum, including the Super XL, picks up all dirt on the first pass. In that case, comparing the old vacuum to the new one on that first pass would be relevant.

Correct answer:
(E)

Answer choice analysis:
(A) Tempting, as this answer seems to suggest the Super XL isn't all that great. However, the argument concludes that the SXL is better, so ignoring the possibility that it also misses some dirt doesn't call the conclusion into question.

(B) Wrong flaw (Temporal). The comparison is being made between these two vacuums, so what will happen in the future isn't relevant. If the comparison was over which model was better, and not over which specific vacuum, then this answer would be more relevant.

(C) Wrong flaw (Bad Generalization). The conclusion would have to state that the SXL is the best vacuum for this flaw to apply; it states only that it's better than one other vacuum.

(D) Wrong flaw. The argument relies on the SXL picking up dirt that the old vacuum missed. The comparison isn't over the amount of dirt picked up, but rather over whether there is dirt that the new vacuum gets to that the old one can't.

(E) Bingo. The "trial" run was off in that the SXL was treated differently than the old vacuum - it was allowed to go second. In order to get a proper comparison, the study would need to reverse the order and compare those results.

Takeaway/Pattern:
When a trial is done, make sure both items being compared are put through the same test. Especially in arguments that deal with ads or salespeople, the LSAT will frequently mess with the way the trial is run to get to the author's preferred conclusion.

#officialexplanation

[jones.mchandler]

I had a really tough time with this flaw question. I missed it during the test, and when I just took 73 again without having reviewed my misses from the initial test. Answer choice D is a very cleverly disguised incorrect answer choice.

The conclusion is the super XL is superior to the old vacuum, because the super XL vacuum picked up the remaining dirt after the old vacuum was used across a dirty area of carpet one time.

My initial thought was that "well, what if the old vacuum picked a greater amount on the first run through the super XL picked up after the old vacuum was used?" D seemed to match this perfectly. However, D is an imperfect translation of my thought, and I'm sure others got trapped the same way. The old vacuum could have picked up more dirt than the super XL...that doesn't weaken the fact the XL picked up the crumbs that the old vacuum left behind.

E is actually how my thought translates into LSAT language. What I needed to realize was that the argument ignores how the two vacuums compare when each vacuum is used to swipe an equally dirty area of carpet.

Simply showing that the XL picks up what the old vacuum left behind does not show that the XL is in fact better...maybe the old vacuum would have also picked up what it initially left behind if it was used in place of the XL.

Really this argument relied on a sort of apples to oranges comparison to justify the superiority of the XL vacuum. E gets at that faulty comparison.

[pewals13]

Here's my amateur take on the question:

First off we're looking for a flaw, the reason why the premises in the stimulus do not logically guarantee the precise wording of the conclusion.

Here's the core I saw:

Super XL picked up dirt your vacuum didn't pick up---------> Super XL is better

(A) Even if dirt remained, the Super XL could still be better, this is not a reason the premises do not justify the conclusion

(D) This doesn't impact the core, even if the other vacuum picked up a greater amount of dirt, this doesn't impact the basis of the conclusion which is the fact that the Super XL picked up different dirt that the other vacuum didn't pick up. Even if this is true, the Super XL could potentially pick up more dirt despite it not doing so in the demonstration.

(E) If this is true, there's no way you can conclude that the Super XL is superior, it would perform the same as the other vacuum.

Additional note: On flaw answers that start with "the author fails to consider" think about what impact the answer would have if the info included was considered, if it significantly weakens the conclusion it is likely your answer

[christine.defenbaugh]

Some great analysis from the both of you!

Really this argument relied on a sort of apples to oranges comparison to justify the superiority of the XL vacuum. E gets at that faulty comparison.

This is really the heart of the issue in the original argument. The premises compare the two vacuums while they are doing two different jobs - a first pass, and a second pass. In order to really justify a conclusion that one vacuum is better than another, we'd need to compare them at the same task!

(A) and (D) are both tempting because they might seem to be revealing a more appropriate comparison: the amount of dirt each leaves behind looks parallel, but that's still the amount left behind after two different jobs; the amount of dirt removed also looks parallel, but again, it's still the amount removed during two different tasks.

Only (E) zeros in on a truly parallel comparison - what if we compared how much dirt is left behind when the two vacuums do the same job.

Great wrong answer analysis, pewals13! And I completely agree with you on this:

Additional note: On flaw answers that start with "the author fails to consider" think about what impact the answer would have if the info included was considered, if it significantly weakens the conclusion it is likely your answer

That's a great way to think about 'fails to consider'/'ignores the possibility' language in flaw questions!

Great work you two!