Critical Reasoning

Source: LSAT

The number of hospital emergency room visits by heroin users grew more than 25 percent during the 1980s. Clearly, then, the use of heroin rose in that decade.

Which one of the following, if true, would account for the statistic above without supporting the author's conclusion?

(A) Widespread use of automatic weapons in the drug trade during the 1980s raised the incidence of physical injury to heroin users.
(B) The introduction of a smokable type of heroin during the 1980s removed the need for heroin to be injected intravenously and thus reduced the user's risk of infection.
(C) Many hospital emergency rooms were barely able to accommodate the dramatic increase in the number of medical emergencies related to drug abuse during the 1980s.
(D) Heroin use increased much more than is reflected in the rate of heroin-linked hospital emergency room visits.
(E) Viral and bacterial infections, malnourishment, and overdose account for most hospital emergency room visits linked to heroin

[spoiler]OA: A. I have tried to put my thoughts in the next post...pls correct me...don't find any correct answer![/spoiler]

Premise: Heroin users' emergency visit increased
Conclusion: use of heroin rose

Question: correct choice will support premise, but, will not support the conclusion

(A) Widespread use of automatic weapons in the drug trade during the 1980s raised the incidence of physical injury to heroin users [spoiler](supports increased visit of heroin users, but, no Support to conclusion about increase in heroin user base. It possible that heroin user base remained same, but, they are not able to bear the drug cost...leading to fight and use of automatic weapons. Or the user base rose incommensurate with the drug availability....so druggists use automatic weapons to get drug) INCORRECT [/spoiler]

(B) The Introduction of a smokable type of heroin during the 1980s removed the need for heroin to be injected intravenously and thus reduced the user's risk of infection.[spoiler](Method to take heroin...not part of the argument...out of scope..INCORRECT)[/spoiler]

(C) Many hospital emergency rooms were barely able to accommodate the dramatic increase in the number of medical emergencies related to drug abuse during the 1980s. [spoiler](increase in heroin users visit...but nothing about user base...INCORRECT)[/spoiler]

(D) Heroin use increased much more than is reflected in the rate of heroin-linked hospital emergency room visits[spoiler].(Heroin user increased...does not mean increase in heroin user base; Visit also did not increase....supports neither premise nor conlusion...INCORRECT)[/spoiler]

(E) Viral and bacterial infections, malnourishment, and overdose account for most hospital emergency room visits linked to heroin.[spoiler](supports only premise...nothing about conclusion...INCORRECT)[/spoiler]

Pls correct me...I don't find any correct answer

I would choose A. This answer illustrates that the number of hospital visits could have increased without the number of heroin users necessarily increasing. If more heroin users get shot, then more will go to the hospital. The stimulus didn't say that they went to the ER because of heroin, it just said the number of ER visits increased

A is correct here. This one brings up a couple of pretty good study points for GMAT CR:

1) Make sure you read the question stem and conclusion very carefully on any of these, because typically that's where people make mistakes, and the GMAT is terrific at subtle wording that makes a big difference. Here, the question stem asks you "which, if true would ACCOUNT FOR the statistic WITHOUT SUPPORTING the conclusion." Basically, your job is to weaken the conclusion using a premise that is consistent with the others.

In your thoughts regarding choice A, you mentioned that you thought it was incorrect because there was "no Support given for the conclusion". Well, that's precisely what the question asked for: ACCOUNT FOR...WITHOUT SUPPORTING. Accordingly, A is correct.

2) Just about every CR problem that involves statistics will include stats that slightly (or sometimes egregiously) miss the mark on the conclusion. Train yourself to note those inconsistencies, quite often make the same mistake that this one did - correlation, but not causation.

Here, just because emergency room visits of heroin users are up does not mean that there are more heroin users. There's correlation, but the logical flaw is that increased heroin usage is not the only logical cause of this statistic. There are at least a few conceivable alternative explanations:

-The heroin trade became increasingly violent in the 80s, leading to more bodily-injury ER visits (like the correct answer choice states)
-Law enforcement was barred from making drug-related arrests in hospitals so that overdose victims would seek medical attention without fear of legal trouble
-More hospitals were built in drug-infested areas, allowing drug users easier access to emergency rooms
-Prior to the 1980s, ER hospitals were not required to offer 24-hour service, meaning that overnight overdose victims did not typically seek ER care.

Any of these above could be reasons that the statistic - heroin-user visits to the ER grew by 25% - could have come to be. If you can learn to spot the correlation-but-not-causation nature of lot of these statistics, and anticipate these alternate explanations, you'll not only do better on the GMAT, but you'll be a better decision maker overall. After all, "save up to $2000" as a sales pitch probably means that: 1) you won't save $2000 ("up to" is the greatest possible savings...most people will save less) and 2) you'll spend a lot more than $2000 to get that "savings". The statistic sounds great, but there may well be an alternative explanation...

For more on this topic, you may want to check out this article: https://www.beatthegmat.com/mba/2010/03/ ... -help-stat

Awesome explanation - Many thanks.

I got this question right and in good time (~46 sec) but I still read your explanation and, must admit, learned a lot. So, I am even more convinced now that one should read such expert explanations even if you know the answer

Thanks, Mylogin (nice screen name, btw!) - I'm glad you think that way. Getting the right answer on a practice question may well be "fool's gold" if you don't quite know why or don't take the time to highlight an important takeaway. Keep reading all of these "expert" explanations...we'll undoubtedly keep writing!