Q6 - A transit company's bus drivers

[kmewmewblue]

I understand the (D) is correct. But, not really sure how I can reach to it logically.

DPB w/ Sup+(D)→DPB normal

How about this? I don't know if I am doing right or not.

Also, when I encounter with the assumption question, I usually try to find the new element mentioned in the conclusion. The new element will not be mentioned in the premises so that answer choice has to have the new element. Can I do this approach in this one? I couldn't really find the particular new element in this conclusion which match to (D).

I really want to nail the assumption question, so if anybody can give me the advice, I really appreciate. Thank you in advance!

[Shiggins]

This is a necessary assumption from how it the question ask for what the argument depends on. This is something the author overlooked or did not shield out of consideration.

You do not have to try a conditional approach. On sufficient assumption questions, they can be more formulaic. The question would ask which "if" assumed.

The conclusion is that the drivers who perform best are the best under normal conditions. We know that the presence of the supervisor will effect them. What is left open in the air is the variability on each individual. What if the best driver gets so nervous from the supervisor he crashes, whereas the worse driver just slightly performs worse.

I hope this helps.

[robowarren]

Thanks for that explanation. I get why D is right, but I am having trouble explaining why C can't be right as well. Is it because it says "most"? I guess I am having trouble what we are trying to bridge here. Thank you for your help.

[jolieyang]

The reason why I crossed out C is when I negated it, it did not completely weaken the argument.

(Negated Answer) For most bus drivers, the presence of a supervisor does not make their performance slightly worse than it otherwise be.

The negated answer still leaves open to the question of how the drivers performance will be affected. Perhaps the supervisor will make their performance significantly worse thereby strengthening instead of weakening the argument.

[ManhattanPrepLSAT1]

Great discussion so far!!

The argument tries to prove that "the drivers performing best with a supervisor aboard will likely also be the best drivers under normal conditions." Why do they say this? Well, all drivers performance is affected by having supervisors on board.

This is not a terrible argument, but there is a big open question. Does the presence of the supervisor affect everyone the same way. Potentially, the best drivers' performance might be more negatively affected by the presence of a supervisor, and so the best drivers with supervisors on board may not be the best drivers under normal conditions.

Answer choice (D) addresses the issue regarding how much each driver's performance is affected.

Incorrect Answers

(A) speaks to the need to put supervisors on board busses to evaluate the drivers' performance. But does not address the argument's conclusion!
(B) speaks to the efficacy of having supervisors evaluate bus drivers' performance, but is irrelevant to the argument's reasoning.
(C) addresses one way in which the drivers could be impacted by the presence of supervisors. But the word most is problematic as it allows some other drivers to not be negatively affected. If these were the worst drivers who were not affected negatively, that could skew the results in such a way that the conclusion may not hold.
(E) speaks to the need to have supervisors evaluate bus drivers, but not whether the best drivers under normal conditions are likely to be the same drivers who perform best with supervisors on board.

[wgutx08]

I disagree that "most" is the problem in C. It makes the statement weaker, but a necessary assumption would still be necessary however weakened in degree. If I need 3 pairs of boots for this winter, of course I will also need 1 or 2 pair!

Translated into this Q, if you add "most" to D, it's still a necessary assumption. "most drivers are affected in roughly the same way"... Yeah, if this is not true, it is even less true that all drivers are affected in the same way, and the original statement will be even less able to stand.

The real problem in C is "slightly". This is really not necessary. Even if all (or most, for that matter) drivers' performance are severely affected, as long as the degree of the effect is the same for all, we can still judge them fairly.

[lissethbayona]

I am a bit confused by the explanation of why (C) is incorrect. From my understanding, in necessary assumption questions, the correct answer will weaken when negated and the others will not. So (C) shouldn't be able to weaken the conclusion at all, right?

I think (C) wouldn't weaken the conclusion because:
If we negate (C) and say, for most bus drivers, the presence of a supervisor DOESN'T make their performance slightly worse, then it would be possible for this portion of bus drivers to include the best and average drivers, while there are some remaining, the worst bus drivers, that ARE negatively affected. In this situation it would still be possible for the argument's conclusion to hold, since the drivers performing best with a supervisor would still be likely also to be the best under normal conditions.

Can someone weigh in and let me know if the negation and rational for (C) are on the right track?

[gaheexlee]

I think (C) wouldn't weaken the conclusion because:
If we negate (C) and say, for most bus drivers, the presence of a supervisor DOESN'T make their performance slightly worse, \

The correct way to weaken (C) would have been to change only the "most" to "less than half."

So you would have: For less than half of the drivers, the presence of a supervisor makes their performance slightly worse.

Why this negation? It's said that there are three types of 'negations' in LSAT: quantifiers, suff/necessary statements, and other 'regular' statements. What you tried was a negation of a 'regular' statement. This particular example however, falls under the first one since 'most' is a quantifier. Just as you would negate the statement "some trees have leaves" by saying "No trees have leaves," so you negate "most trees have leaves" by saying "less than most trees have leaves."

Hope that helped!

[JorieB701]

I am a bit confused by the explanation of why (C) is incorrect. From my understanding, in necessary assumption questions, the correct answer will weaken when negated and the others will not. So (C) shouldn't be able to weaken the conclusion at all, right?

I think (C) wouldn't weaken the conclusion because:
If we negate (C) and say, for most bus drivers, the presence of a supervisor DOESN'T make their performance slightly worse, then it would be possible for this portion of bus drivers to include the best and average drivers, while there are some remaining, the worst bus drivers, that ARE negatively affected. In this situation it would still be possible for the argument's conclusion to hold, since the drivers performing best with a supervisor would still be likely also to be the best under normal conditions.

Can someone weigh in and let me know if the negation and rational for (C) are on the right track?

This is old but I felt compelled to clarify something here lest others be confused. For necessary assumption questions, the correct answer will not just weaken an argument when negated, it will blow it up, entirely. So, yes it weakens the argument but it weakens it all the way - it doesn't just put a dent in it or call it into question. You can think of it like this:

A sufficient assumption is one that if true, the argument wins. A necessary assumption is one that if not true, the argument loses.

So here, if the argument is that everyone's performance is affected, therefore the best are still the best... it is necessary that they are all affected in roughly the same way and to the same extent. Because if it's not true that they are all affected similarly, then an argument claiming that the assessments are still indicative of performances without the supervisor being there, is total garbage. You can and often should negate arguments as shown above^^^, and I'm sure there are toughies out there where this would be super important to finding the right answer, but sometimes it's just easier to say, "It is not true that.... (and then fill in whatever the answer choice says)."

If you did this for C you would say, "It is not true- that for most drivers, the presence of a supervisor makes their performance slightly worse than it otherwise would be."

To which the transit company dude making the argument would say, "So, what? My argument is still valid." Because it's not necessary that everyone's performance is slightly worse.. it's also possible that their performances were all MORE than slightly worse. We care if their performance was affected but we do not care the degree to which it was.

[CharlesS800]

I began this question by considering the argument. I settled on:

Supervisor presence affects every driver's performance ---> Drivers preforming the best with the supervisor will also be best under normal circumstances

Considering the gap in this argument, what I came up with was, well what if some drivers do way better with supervisor aboard than otherwise. A continuation of this would be saying that drivers do not all do as well or as worse in the presence of evaluators.

With this in mind, I proceeded to the answer choices.

I tossed A and B immediately as out of scope to the argument.

C seemed somewhat relevant so I kept it around. Ditto with option D.

I also got rid of option E because it was out of scope.

I then negated both remaining answer choices. I also did fall into a trap that others seemed to as well and incorrectly negated answer choice C. However, even with this incorrect negation, it was clear that answer choice D blew up the argument and was, conveniently enough, relatively in line with my prephrase. Big takeaway on this: negate answer choices correctly so that on a tougher question, an answer choice like C that could be correct is not incorrectly discarded.