I chose A and correct answer is B. I rember this problem form OG11 (not the answer though) so I went there to check the explanation but it didnt convince me at all. I guess I dont understand it. I think B is "so obvious" it does not say anything new.




Any comments about this one?

Thanks

Hi, Luci - sorry this one got lost in the madness of the past week!

Summary:
3% of all equipped with detectors
33% of vehicles caught speeding equipped with detectors
Conclusion: drivers who use detectors are more likely to speed regularly than those who don't

Author has made a leap between speeding only occasionally and getting (unluckily) caught vs. speeding regularly - but the rest of the argument does not actually mention anything about the frequency of speeding of various groups. It may be obvious that the more often you speed, the more chances you have to get caught - but the argument does not spell this out.

Choice A does not address author's conclusion - he's contending that drivers who choose to use detectors do so because they plan to speed regularly. This choice says that whether someone has a detector has a bearing on whether s/he gets caught - which may be true in the real world, but it does not answer this question.

Choice B addresses this leap that the author makes about the frequency of speeding. If drivers who are ticketed are likely to exceed the speed limit regularly, then the 33% of vehicles caught speeding with detectors will fall into this category of people who are more likely to speed regularly. Remember, again, that it may be obvious that the more often you speed, the more likely you are to get caught - but the argument doesn't literally spell it out, and that's the point. The author is just assuming this point is true without spelling it out.

_________________
Stacey Koprince
Instructor
Director of Online Community
ManhattanGMAT

Can someone explain why D is incorrect?

Thanks.

hey -

d is incorrect because its content is irrelevant to the content of the passage.

the passage talks in terms of percentages of the number of VEHICLES ticketed - not percentages of the total number of tickets. therefore, even if certain vehicles were ticketed multiple times, nothing in the argument would change (because one vehicle still counts as one vehicle, even if it is pulled over multiple times).

also note that you're looking for an ASSUMPTION that is REQUIRED by the passage. if you pick an answer like d - which is clearly not REQUIRED by the argument, even if you don't immediately see why it's irrelevant - that probably means you aren't reading the question prompt correctly.

Hi,

Can I conclude that the premise -- 3% vs. 33% stats -- can be used to conclude that vehicles with a radar detector are more likely to speed than vehicles without a radar detector are?

Thanks in advance.

no.

that still requires an assumption that "drivers who speed" is equivalent to, or proportional to, "drivers who receive speeding tickets".
there is no evidence in the passage for such an equivalence or correlation, so your conclusion would be out of scope.

remember, you have to achieve TOTAL DISCONNECT between topics that are not
1) exactly the same
or,
2) STATED IN THE PASSAGE to be equivalent.

for instance, you have to think of, say, "murderers" and "people convicted of murder" as COMPLETELY DIFFERENT unless the passage states their equivalence.
this is at best difficult, but you have to try to think this way; otherwise you'll find yourself making all sorts of assumptions that you're not allowed to make.

Hi Ron,

In another post, you mentioned that for each CR question, I should be able to fill in the blank in "if i see ______ ON ANOTHER PROBLEM, i should ______".

What can I fill in for this question? Just want to learn how to summarize CR questions.

Thanks in advance.

One possibility: ""if i see NUMBERS/DATA GIVE on another problem, i should JOT THOSE DOWN IN AN ORGANIZED WAY."

Of course, there are many possible takeaways. What you focus on depends on what may have tripped you up in the problem. If you missed this one because you are not clear as to your assumption types, perhaps that will become your focus, etc.

Thanks Jonathan.
Is it possible to be a little bit more specific but generalize the pattern?
Thanks in advance.

Hi HM,

So, what I meant by last night's post was that one possible takeaway is:

"Hey, this problem hinged on some pretty specific data. If I had jotted that data down in an organized way, it might have really helped me to understand the mechanics of the problem. So, in the future, when I see specific data given (numbers, dates, etc.), I should probably jot that stuff down for myself."

Of course, the above would only be your note to yourself if you hadn't done that the first time around.

You had asked earlier on for an example of the type of thing you would note for yourself in regards to any specific problem. Of course, what you note (or make a flashcard out of, etc.) is very dependent on what went wrong for you the first time you saw that problem. While there are general takeaways, those you can learn from the books, etc. Your own specific takeaways are more of a personal thing.

Hope that helps : )

I'm confused with this question. Previously, I confused 'regularly' with 'repeatedly'. But now I'm confused with how the conclusion can be true with (b) as assumption.

According to (b), If those 33% fall into 'speed regularly' category then the other 67%, who don't have detectors, would also fall into 'speed regularly' category. Now, how can I conclude that drivers who are equipped with radar detectors (3% vs. 33%) are more likely to 'speed regularly' than other who are not (97% vs. 67%). I mean how can I compare both groups without any solid numbers.

no, no, you're completely ignoring what is most important about that correct answer choice.

the existing problem with the passage is that it conflates "people who are ticketed for speeding" with “people who speed regularly”.
since these two things are, in fact, not the same, we need an assumption that the group of people ticketed for speeding actually represents people who speed more often.

--

you would need the same type of assumption if, e.g., the premises of the argument talked about “people convicted of crime X” but the conclusion talked about “people who have committed crime X”.

Ron, Stacey -- thanks for the succinct explanations.

D is a great trap answer. basically, are you saying that % of vehicles ticketed and % of tickets are 2 different statistics? and what D is saying is that many vehicles ticketed for exceeding speeding limit were caught multiple times. does this mean many vehicles caught for speeding have a tendency to speed more often or just that these people were over-represented?

_________________
Ashish
Share why wrong answer(s) are not right than just stating why the right one is.

i think A could be a WEAKENER rather. from what i see, the premises can have two distinct possibilities:
1. drivers who equip their vehicles with detectors tend to speed on a regular basis than drivers who do not (the conclusion here)
2. it was a chance occurrence that a relatively higher percentage of drivers who equip their vehicles with detectors were caught speeding than were drivers who do not (counter-conclusion)

A is saying that drivers who equip their vehicles with detectors are less likely to be ticketed than are drivers who do not, meaning drivers who equip their vehicles with detectors are lucky enough not to get caught and thus, negating the possibility 1. and making the counter-conclusion 2. more likely.

does this make sense?

_________________
Ashish
Share why wrong answer(s) are not right than just stating why the right one is.

no, if this were a strengthening/weakening problem, then choice (a) would be a strengthener; if people driving with radar detectors were actually less likely to be caught and ticketed, then the 33%/3% discrepancy described in the passage would actually take on even more significance.

the problem, though, is that you are approaching this problem from the wrong angle: you're trying to approach it as though it were a strengthening/weakening problem.
it's not.
an assumption is not the same thing as a strengthener!
the vast majority of strengtheners are NOT assumptions!

an assumption is a statement that is REQUIRED in order for the argument to work. (if you have a statement that considerably strengthens the argument, but isn't actually REQUIRED, then it's not an assumption. period.)
this assumption treats the population of drivers who are ticketed for speeding as a reliable representation of the general population of speeders. although this may seem “obvious” to you, it is still a required assumption!