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Some doctors believe that a certain drug reduces the duration

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Some doctors believe that a certain drug reduces the duration [#permalink]

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Some doctors believe that a certain drug reduces the duration of episodes of vertigo, claiming that the average duration of vertigo for people who suffer from it has decreased since the drug was introduced. However, during a recent three-month shortage of the drug, there was no significant change in the average duration of vertigo. Thus, we can conclude that the drug has no effect on the duration of vertigo.

Which one of the following is an assumption required by the argument?

(A) If a drug made a difference in the duration of vertigo, a three-month shortage of that drug would have caused a significant change in the average duration of vertigo.
(B) If there were any change in the average duration of vertigo since the introduction of the drug, it would have demonstrated that the drug has an effect on the duration of vertigo.
(C) A period of time greater than three months would not have been better to use in judging whether the drug has an effect on the duration of vertigo.
(D) Changes in diet and smoking habits are not responsible for any change in the average duration of vertigo since the introduction of the drug.
(E) There are various significant factors other than drugs that decrease the duration of vertigo for many people who suffer from it.

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[Reveal] Spoiler: OA

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Re: Some doctors believe that a certain drug reduces the duration [#permalink]

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New post 14 Aug 2017, 21:32
A
Was stuck between A and C.
But on negating A seemed to have a much more effect on the conclusion than C.
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Re: Some doctors believe that a certain drug reduces the duration [#permalink]

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New post 16 Aug 2017, 10:28
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Some doctors believe that a certain drug reduces the duration [#permalink]

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New post 16 Aug 2017, 11:54
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Hi Experts GMATNinja GMATNinjaTwo mikemcgarry
Is below approach correct:
main conclusion:
the drug has no effect on the duration of vertigo
What leads to this conclusion:
a. Initially it was believed by few docs that certain drug reduces the duration of episodes of vertigo. This led to another intermediate claim that since the drug was introduced, the average duration of vertigo for people who suffer from it has decreased
b. Counter premise suggests that in spite of shortage of drug in past 3 months there was no change in average duration of vertigo. This is interesting since ideally average duration of vertigo must have been increased in past three months due to shortage of drug if docs claim is true.

Method to look for assumption: there are no other circumstances than shortage of drugs that lead to drugs having an effect on vertigo duration

POE:
(A) If i negate this:
If a drug made a difference in the duration of vertigo, a three-month shortage of that drug would have caused a same average duration of vertigo as in earlier time (ie without shortage) or even less duration of vertigo. In this case, since some change is indeed happening (concentrate on possibility of less duration) it leads to claim that drug does have an effect on duration of vertigo hence my conclusion breaks down on negating this optoin

(B) we are concerned with last three months shortage in drug not since introduction of drug.

(C) tricky one, so let me try to negate it:
A period of time greater than three months would have been better to use in judging whether the drug has an effect on the duration of vertigo.
not sure of we are concerned with effectiveness of drug wrt past three months or greater time period

(D) seems to be a strengthener not an assumption, it is a may be true statement, not must be true

(E) same as (D)
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Re: Some doctors believe that a certain drug reduces the duration [#permalink]

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New post 17 Aug 2017, 14:31
Masshole, Hi,
Can you please post the OE. I got the answer correct, but want to review the explanation. Thanks in advance.

Some doctors believe that a certain drug reduces the duration of episodes of vertigo, claiming that the average duration of vertigo for people who suffer from it has decreased since the drug was introduced. However, during a recent three-month shortage of the drug, there was no significant change in the average duration of vertigo. Thus, we can conclude that the drug has no effect on the duration of vertigo.

Which one of the following is an assumption required by the argument?

(A) If a drug made a difference in the duration of vertigo, a three-month shortage of that drug would have caused a significant change in the average duration of vertigo.
(B) If there were any change in the average duration of vertigo since the introduction of the drug, it would have demonstrated that the drug has an effect on the duration of vertigo.
(C) A period of time greater than three months would not have been better to use in judging whether the drug has an effect on the duration of vertigo.
(D) Changes in diet and smoking habits are not responsible for any change in the average duration of vertigo since the introduction of the drug.
(E) There are various significant factors other than drugs that decrease the duration of vertigo for many people who suffer from it.
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Re: Some doctors believe that a certain drug reduces the duration [#permalink]

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New post 17 Aug 2017, 22:24
Imo A
A and C are close contenders but I will vouch for A
If suppose the period is 6 months long and we witness episodes of vertigo among people then this choice fails and the conclusion drawn is not good .
If there are no effects then the conclusion drawn is correct .therefore C is of no help to us .
A is much better and direct .

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Re: Some doctors believe that a certain drug reduces the duration [#permalink]

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New post 24 Aug 2017, 15:13
adkikani wrote:
Hi Experts GMATNinja GMATNinjaTwo mikemcgarry
Is below approach correct:
main conclusion:
the drug has no effect on the duration of vertigo
What leads to this conclusion:
a. Initially it was believed by few docs that certain drug reduces the duration of episodes of vertigo. This led to another intermediate claim that since the drug was introduced, the average duration of vertigo for people who suffer from it has decreased
b. Counter premise suggests that in spite of shortage of drug in past 3 months there was no change in average duration of vertigo. This is interesting since ideally average duration of vertigo must have been increased in past three months due to shortage of drug if docs claim is true.

Method to look for assumption: there are no other circumstances than shortage of drugs that lead to drugs having an effect on vertigo duration

POE:
(A) If i negate this:
If a drug made a difference in the duration of vertigo, a three-month shortage of that drug would have caused a same average duration of vertigo as in earlier time (ie without shortage) or even less duration of vertigo. In this case, since some change is indeed happening (concentrate on possibility of less duration) it leads to claim that drug does have an effect on duration of vertigo hence my conclusion breaks down on negating this optoin

(B) we are concerned with last three months shortage in drug not since introduction of drug.

(C) tricky one, so let me try to negate it:
A period of time greater than three months would have been better to use in judging whether the drug has an effect on the duration of vertigo.
not sure of we are concerned with effectiveness of drug wrt past three months or greater time period

(D) seems to be a strengthener not an assumption, it is a may be true statement, not must be true

(E) same as (D)


adkikani, nice analysis! I just have a few comments...

  • In part (a) under "What leads to this conclusion:", your analysis seems to suggest the belief of the docs LED to the claim that "the average duration of vertigo for people who suffer from it has decreased since the drug was introduced." The second part is really the evidence on which the belief of those docs is based.
  • Be careful when negating choice (A) (or any answer choice for that matter). If negated, choice (A) becomes, "If a drug made a difference in the duration of vertigo, a three-month shortage of that drug would NOT have caused a significant change in the average duration of vertigo." If that were the case, it would make the following evidence irrelevant: "during a recent three-month shortage of the drug, there was no significant change in the average duration of vertigo." The author's conclusion is based on that evidence, so (A) is necessary assumption.
  • As for choice (C), you negated it properly ("A period of time greater than three months WOULD have been better to use in judging whether the drug has an effect on the duration of vertigo." But this would not affect the author's argument. Even if a longer time period would have been better, that doesn't change the following evidence: "during a recent three-month shortage of the drug, there was no significant change in the average duration of vertigo." The author's conclusion is based on that evidence, so choice (C) is not a required assumption.

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Re: Some doctors believe that a certain drug reduces the duration [#permalink]

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New post 11 Sep 2017, 09:01
Quote:
The argument here is that a drug purported to shorten bouts of vertigo does not actually do so. The evidence? That during a 3-month shortage of the drug, the duration of patient's bouts of vertigo did not change.

There are two assumptions here that you may have noticed (and perhaps others):
1. That the drug's affect appear or disappear within 3-months. Maybe it takes 5 months for the drug to build up enough presence in one's system to affect a change, and a similar length of time to dissipate.
2. That the average duration of the bouts of vertigo is an accurate measurement -- perhaps there were other factors in the environment that lengthened duration for others?

(A) plays on the issue in #1 above. The argument can be stripped down to:
No change --> Not effective, and (A) provides the contrapositive: Effective --> Change

If we were to negate (A) and state that if the drug were effective we would not see a change, then the argument becomes invalid. The overall efficacy and the change witnessed after a shortage would be "unhooked."

As for the incorrect answers:

(B) is tempting. If provides Change --> Effective, which is the reverse of the contrapositive, and so it does not help us. Put simply, we are interested in the effects of there not being a change, not what happens if there were a change.

(C) may be true -- perhaps 4 months would be a better test. But because a fact is less useful than another does not mean it is not true or useful. A DNA match might be better than a fingerprint, but that doesn't mean that a fingerprint is useless or not enough to convict.

(D) is irrelevant. Even if those other factors are relevant, we don't know that the drug is irrelevant. When we negate (D)--diet or smoking does change the duration of vertigo--it actually bolsters the conclusion that the drug has no effect.

(E) is similarly irrelevant. Whether there are significant factors other than the drug does not affect whether the drug is effective.

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Some doctors believe that a certain drug reduces the duration [#permalink]

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New post 13 Sep 2017, 11:14
Some doctors believe that a certain drug reduces the duration of episodes of vertigo, claiming that the average duration of vertigo for people who suffer from it has decreased since the drug was introduced. However, during a recent three-month shortage of the drug, there was no significant change in the average duration of vertigo. Thus, we can conclude that the drug has no effect on the duration of vertigo.

Conclusion
A confusion is created in the argument , first by saying "certain drug reduces the duration of episodes of vertigo" and second by saying "the drug has no effect on the duration of vertigo". This makes it a little hard to connect the conclusion with the given premises.
Notice two things carefully in the above argument:
1. the author uses "certain drugs", which means that not all drugs has the given affect.
2. "Some doctor believe".
So, we may pre-think the following:
1. people took those drugs that is believed to have the required affect.
2. The period of 3 months is enough to show that the drug has no effect on the duration of vertigo.
3. The drug is actually not effective from the time people started taking it.

Which one of the following is an assumption required by the argument?

(A) If a drug made a difference in the duration of vertigo, a three-month shortage of that drug would have caused a significant change in the average duration of vertigo.
-This validates one of the assumption. So, this may be the answer. I'm still confused.
(B) If there were any change in the average duration of vertigo since the introduction of the drug, it would have demonstrated that the drug has an effect on the duration of vertigo.
- This contradicts the premise because the premise already says that certain drug has already reduced the duration of vertigo and hence has shown the effect.
(C) A period of time greater than three months would not have been better to use in judging whether the drug has an effect on the duration of vertigo.
- This might seem confusing at first. However, if we consider that the drug takes four months to show any change in duration of vertigo, can we still prove that the drug has no effect on the duration of vertigo? We can not, as the drug may or may not show the expected result in change in duration of vertigo even after four months.
(D) Changes in diet and smoking habits are not responsible for any change in the average duration of vertigo since the introduction of the drug.
- We are dealing with something that is put of scope- diet, smoking . The argument does not care about all these.
(E) There are various significant factors other than drugs that decrease the duration of vertigo for many people who suffer from it.
Out of scope. Factors other than drugs that decrease the duration of vertigo, doe not prove that the drug is not able to reduce the duration of vertigo. There may be other factors that can decrease the duration of vertigo, while the drug may still can have the effect.
So, A is the right answer.
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