A year ago, in response to ongoing complaints of pickpocketing at New

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Update the main post with the intent to gather all Ron's Questions. Bookmark it if you wanna

https://gmatclub.com/forum/ronpurewal-o ... l#p1892383

Regards

D seems to be the best choice. Patting down the pockets may not only draw the attention of the pick-pocketers but also reveal immediately to the passenger whether the valuables are safe in the pockets. If not, he is going to report the loss of valuables at the station.

A year ago, in response to ongoing complaints of pickpocketing at New City’s busy central train station, the city’s police department erected prominent signs throughout the train station warning passengers to beware of pickpockets. As soon as the signs were erected, however, the reported incidence of pickpocketing, per passenger, at the station immediately rose to three times the previous rate—and stayed at the new, higher figure until the signs were removed six months later. As soon as the signs were removed, the per-passenger rate of reported pickpocketing incidents returned to its original level, as quickly as it had risen when the signs were first posted.

Which of the following, if true, does the most to explain the surprising trends in the per-passenger rate of pickpocketing reported at New City’s central train station?

A. In the vast majority of reported incidents of pickpocketing at the station, the victim is traveling during the morning or evening rush, when the station is especially crowded. Does not explain anything

B. New City’s police department almost never investigates reports of pickpocketing, nor do insurance policies typically provide any compensation for items stolen in a public place.Out of scope

C. New City’s train fares, formerly paid with cash in the boarding areas, must now be paid with electronic fare cards sold outside the stations; the signs were posted during the transition period when both means of payment were accepted.Out of scope

D. A large proportion of passengers, upon reading the signs, would briefly pat down the pockets holding their wallets or other valuables, even if they had to stop walking and put down their baggage to do so. correct answer because on seeing the sign peopple will pat the pockets where they had kept the valueables but by doing so they would also fall victim to pickpocketer who is watching them becasue then the pickpocketer would know where his victim has kept all the valueables.

E. Rising gasoline prices, along with an explosion of new high-density housing within walking distance, have nearly doubled the number of passengers using the station per day since last year. out of scope

Here's an answer key.

__

We’re asked to explain the “surprising trends” (plural) in the frequency of reported incidents of pickpocketing at New City’s main train station. There are two trends, both statistically related to the presence of temporary signs warning passengers to beware of pickpockets:
• When the signs were erected, the reported incidence of pickpocketing tripled IMMEDIATELY.
• As soon as the signs were removed, the rate returned to its original level, just as quickly.
We need outside information that helps to explain both of these surprising trends.

It’s possible that the two trends could have happened for entirely different reasons. However, given that (i) the elevated rate of reported pickpocketing coincided exactly with the presence of the signs and (ii) the rate returned to exactly its original level once the signs were gone, we can safely dismiss this possibility. (Correct answers will not depend on extraordinarily improbable coincidences.)

So, we need some circumstance, simultaneous with the presence of the signs, that can reasonably explain why there were three times the usual number of reports of pickpocketing, per passenger, during that period only.
A correct answer could do either of two things:
• It could give a reason why passengers were 3 times as likely to actually be pickpocketed while the signs were posted;
• It could give a reason why passengers were 3 times as likely to report having been pickpocketed during that period.
Use these as STANDARDS by which to judge the answer choices.

A/
This statement would be relevant only if a drastically different proportion of passengers traveled at peak hours during the period when the signs were posted. No such change is described or implied, so this choice is irrelevant.

B/
This choice means, essentially, that pickpocketing victims have NO economic motivation to file a report.
If victims could recover (at least some of) their losses as a result of reporting the theft — whether from the thief, if she/he were caught, or by submitting the report to an insurer — then the signs might, by reminding the victims of this, encourage more such reports. If victims have no reasonable chance of being reimbursed, though, then that eliminates this consideration (which is already very weak) as a possible explanation.

C/
Switching from cash to electronic fare cards would, if anything, decrease the frequency of pickpocketing — simply because passengers would no longer have to carry cash in an immediately accessible place. Therefore, if this statement is true, we would expect a gradual decline in pickpocketing throughout the transition period, as fewer and fewer passengers would pay with cash — AND we would expect the theft rate to settle at a level lower than its pre-transition value. So, this statement does not adequately explain either trend.
(Even if the use of fare cards somehow made pickpocketing more likely — already an implausible suggestion — neither the drop in thefts nor the abruptness of either change would be any easier to understand.)

D/
If this statement is true, then, as they passed through very specific areas of the station (= near the signs), a large proportion of passengers would inadvertently indicate the EXACT location of their valuables to anyone who might be watching.
It’s possible, of course, that this “spot checking” could have made the passengers themselves more alert, too — but those who had to stop and put down their luggage could not possibly have maintained the same degree of vigilance once in motion again.
Thus, according to this choice, the signs ultimately made pickpockets both more accurate and more efficient.

E/
The passage quotes crime rates per passenger using the station, so the absolute number of passengers is irrelevant.
Even if increased crowding led to a disproportionate increase in pickpocketing — a reasonable supposition, which would cause per-passenger theft rates to increase — this choice does nothing to explain why the theft rate dropped after a certain period. Nor does it explain the abruptness of either change.

The correct answer is D.

A couple of posters on this thread have classified choice C as a "contender" for some reason or another—but that shouldn't be so.

Check out the answer key for a more detailed explanation—but, basically, there's no reason to think switching to electronic fare cards would lead to an increase in pickpocketing. (If anything, it would be more likely to decrease pickpocketing, since fewer and fewer people would be using cash in plain sight of others!)
And beyond that, there are two other problems:
• Any changes would be gradual—not abrupt and immediate, as these changes are described;
• If one form of payment were more conducive to theft than the other, then, the final rate of pickpocketing would, accordingly, be DIFFERENT from the starting rate.

Basically, for choice C, the rate of pickpocketing (and/or reports thereof) would follow one of these two types of curves, over the transition period:





...where the first is more reasonable (since, again, electronic cards would be much more likely to curb pickpocketing than to foster more of it).

The middle parts of the graphs don't need to be straight lines; it's the overall relationship (increase/decrease) that matters.

EDITED — originally posted wrong link



^^ No need to bookmark that problem. This one is an improved version of that one (which, upon review, had some noticeable faults).

It may even be a worthwhile exercise to examine what I changed—and consider WHY I made those changes. (The change from "subway" to "train station" has no functional significance, but, basically every other change was made for some reason or another.)
If you can understand why I made the changes I made to the problem, your overall intuition for the functionality—and rigor—of CR problems could benefit.

Hey Ron, good to see you, hope you've been doing well!

I wrote a post in that earlier thread about some of the issues with the first version of this problem, if anyone is curious, though as Ron suggests, you'll learn most by thinking about it on your own first, before reading an explanation. The new version of the question posted here doesn't have any logical issues, so it's a much better question.

Hi RonPurewal - If you have edited the question in the same post, the book mark will reflect the updated version! Happy to take a look at the previous version, if you don't mind re-posting it on the same thread.

I think Ron accidentally responded to the wrong comment -- he was talking about the similar problem that nguyendinhtuong pointed out:

Got it..SarahPurewal - thanks!

Thanks Ron

The answer choices can be easily narrowed down to C and D.

C) if electronic payment method led to decline in pick pocketing, it should drop to 0 level - that is even after transition some level of pick pocketing is still happening. Incorrect.

D) seems right. We need to justify why on removing the sign, the incidents of reporting returned to original level that is before the signage was put up. This implies the reason for spike in incidents is something to do with signage. Choice D clearly identifies that. Correct choice.



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dear experts, RonPurewal, GMATNinja, gmat1393, GMATNinjaTwo, @nightblade354,@SarahPurewal

I compared with these two CR questions,
I found some difference,
#1 response to the complaints VS response to the number
#2 signs stays there VS sings erected first and then removed
#3 rate changed immediately VS rate changed but no mentioned immediately.
# reported pickpocketing, VS pickpocketing,

I haven't yet figured out the rigor of CR questions based on these difference what I realized.
I have studied GMAT for many years, but seems little progress. I don't know what I missed.
when I read this thread, I think I need spend more time to analyze the questions, but I am still clueless, would you please give some hints?

thanks in advanced.

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