People who live unusually long tend to have been lean young adults who

Question

People who live unusually long tend to have been lean young adults who went on to gain approximately one pound every year, so lean young adults can improve their chances of living a long life by gaining about a pound every year.

A flaw in the argument above is that it

(A) gives reasons for the truth of its conclusion that presuppose the truth of that conclusion

(B) proceeds as though a condition that by itself is enough to guarantee a certain result must always be present for that result to be achieved

(C) assumes without proof that two phenomena that occur together share an underlying cause

(D) concludes that one phenomenon is the cause of another when at most what has been established is an association between them

(E) fails to recognize that a tendency widely shared by a subgroup within a given population will not necessarily be widely shared by that population as a whole

jns · Accepted Answer

A - lean young adults. B - people who live long. C - adults who gained one pound every year.
Premise: B  tend to  have been (usually are) A who became C. B=A+C
Conclusion: A  can  become B  if  they become C too. A-> B, if A+C

A. reasons for the truth of conclusion (premise) presupposes (requires) the truth of conclusion. No, premise does not require the conclusion to be true. Rather, the conclusion is clearly derived from the premise.
B. there is no guarantee in the argument anywhere. 'Tends to' does not indicate a guarantee.
C. Proof is provided. Also, it is unclear which two phenomena occur together and which one is the cause? A and B do not occur together. There is a 'if' relationship between A and B which makes them sequential.
D.  Correct . Concludes that combination of A and C causes B, whereas 'tends to' in the premise indicates only a weak association. So does 'can improve' in conclusion.
E. The conclusion restricts itself to lean people. Population as a whole is not referred to anywhere in the argument.

MagooshExpert · Answer

Hi TaN1213 , Carolyn from Magoosh here -- I can step in for Mike

The wording here is all a bit complicated here, so it's important to really read the answer choices carefully. When we do that, we find that B does not quite fit the situation that we're talking about. Let's think about this argument. There is an observation that people who live for a long time started out lean and then gained about a pound every year. So there is an association made: gain one pound every year <--> live long. The argument then says that if someone wants to live long, they should gain one pound every year. In order to make that conclusion, we need to turn that association into a cause-and-effect: gain one pound every year --> live long. This, of course, is a fallacy. And that fallacy is perfectly described by option D here. Now, B is talking about a condition that must be present in order for a result to be achieved. Look at the first part: "a condition that by itself is enough to guarantee a certain result". What is that condition, in this context? There isn't one -- we don't know of any condition here that by itself will guarantee that someone will live long. We know that there is an association with gaining one pound every year, but we certainly can't say that this is guaranteeing that someone will live for a long time. So even without reading the second half of B, we know that this answer choice cannot be correct. There simply is no condition mentioned here that by itself can guarantee that someone will live for a long time. I hope that helps!

-Carolyn

d3thknell · Answer

the stem has a construction - since A tends to B so B must tend to A.
this is faulty and both options B and D seem to fit the bill.
i chose D though since it seemed better,but still need clarification why B is wrong.

TaN1213 · Answer

People who live unusually long tend to have been lean young adults who went on to gain approximately one pound every year, so lean young adults can improve their chances of living a long life by gaining about a pound every year.
A flaw in the argument above is that it

(B) proceeds as though a condition that by itself is enough to guarantee a certain result must always be present for that result to be achieved

(D) concludes that one phenomenon is the cause of another when at most what has been established is an association between them

Although D can be credited as correct, B has a more logical reasoning. 
 mikemcgarry ,

Would you please assist in understanding why is B wrong?
Thank you

TaN1213 · Answer

Hello Carolyn,

Please find my understanding of B :
 
A  flaw  in the argument above  is that it "proceeds as though  a condition that by itself is enough to guarantee a certain result must always be present for that result to be achieved"

The B states the  flaw   as though( assuming  ) the following is correct :
The action of gaining approximately one pound every year(a condition) that by itself is enough to guarantee a longer lifespan (a certain result) must always be present for actually getting a longer lifespan(result to be achieved).

The bold 'as though' part is the  flawed assumption  that is stated in B. For example: Everyone greeted Garry as though he is the owner of the casino. This is the flawed assumption implied by 'as though'. It does not mean that this sentence is telling that Garry himself was the owner of the casino. Similarly, B is  not  talking about a condition that  must  be present in order for a result to be achieved. B states the flaw.

By the way, just wondering where is Mike. Since quite many days, I haven't had seen him around in the gmatclub. I hope he is doing well.

Thank you.
  GMATNinja , your insight is much appreciated.
Thank you.

MagooshExpert · Answer

Hi TaN1213 , Mike is currently working on other projects at Magoosh, and so won't be posting on GMATclub much for now. Thanks for clarifying your reasoning

Let's use a different example to understand this better, since the wording here can get a little complicated. Say we have a statement like: John incorrectly assumes that his ice cream, which is chocolate, is dairy-free. Now, the incorrect assumption here is that the ice cream is dairy-free . It is NOT that the ice cream is chocolate . The fact that the ice cream is chocolate is not part of his assumption -- it is something that this statement is assuming is fact. So according to this statement, there is no question that the ice cream is chocolate. If the ice cream is not in fact chocolate, then this entire statement no longer applies, because it does not match the situation. If John's ice cream is vanilla, this statement doesn't make sense. His assumption is only that the ice cream is dairy-free . Now let's look at our actual statement: B assumes that the action of gaining approximately one pound every year (a condition) that by itself is enough to guarantee a longer lifespan (a certain result) must always be present for actually getting a longer lifespan (result to be achieved). So, the "which is chocolate" part is analogous to "that by itself is enough to guarantee a longer lifespan". It is NOT part of the assumption -- it is something that must be true in order for the statement to make sense. However, this is not true. Gaining approximately one point every year is NOT enough to guarantee a longer lifespan by itself. This is like saying that John's ice cream is vanilla. It makes the entire statement irrelevant to our situation, because it is simply not true. Here, the only assumption is that the action of gaining approximately one pound every year must always be present for getting a longer lifespan. In your second example, there isn't an analogous part. Let's modify it to say: Everyone greeted Garry as though he is the owner of the casino, since he spends so much time gambling. The assumption here is still just that Garry is the owner of the casino. The fact that he spends so much time gambling is NOT part of the assumption -- it is something that must be true in order for this statement to apply. So let's say that Garry actually never gambles. Then, this statement will simply not apply; it no longer makes any sense. If Garry never gambles, then it's not that people are making an incorrect assumption -- the facts are just totally wrong. Does that help to clear things up any more here? If not, let me know

-Carolyn

Skywalker18 · Answer

People who live unusually long tend to have been lean young adults who went on to gain approximately one pound every year, so lean young adults can improve their chances of living a long life by gaining about a pound every year.

A flaw in the argument above is that it

(A) gives reasons for the truth of its conclusion that presuppose the truth of that conclusion - Incorrect

(B) proceeds as though a condition that by itself is enough to guarantee a certain result must always be present for that result to be achieved - Incorrect - we are told about a correlation and it has not been mentioned as necessary condition

(C) assumes without proof that two phenomena that occur together share an underlying cause - Incorrect - no such underlying cause is mentioned

(D) concludes that one phenomenon is the cause of another when at most what has been established is an association between them - Correct - this explains correlation vs causation

(E) fails to recognize that a tendency widely shared by a subgroup within a given population will not necessarily be widely shared by that population as a whole - Incorrect - this option seems incorrect if we consider the population as all adults (or humans) and the subgroup within a given population refers to lean young adults.

But what If we consider the population as the lean young adults and the subgroup as the population of lean young adults with a tendency to gain approximately one pound every year and thus live a long life? Won't E make sense then?

AjiteshArun  ,  GMATNinja  ,  MagooshExpert  ,  GMATGuruNY  ,  VeritasKarishma  ,  DmitryFarber  ,  ChiranjeevSingh  ,  RonPurewal  ,  VeritasPrepBrian  ,  MartyMurray  ,  ccooley  , other experts - please enlighten

AjiteshArun · Answer

When they say "people who...", we should look at that group as all people who live unusually long. Many,  but not all , people in this group were generally lean when they were young adults, and they had gained ~1 pound every year. So we can't say that the population consists of only those people who were lean as young adults.

teaserbae · Answer

AjiteshArun  
Can you please brief the option A ?
I didn't even understand the option

AjiteshArun · Answer

When we say something like  the premise presupposes the truth of the conclusion , what we mean is that the premise takes the conclusion as a given. For example:

A high GMAT score is essential   because   it is necessary to get a high GMAT score .

Namangupta1997 · Answer

AjiteshArun

The passage starts by people who live "unusually" long so we are therefore talking about a group of people that is definitely not the majority. This minor population group has a tendency X -->  they used to be lean young adults who went on to gain approximately one pound every year.   
In the second part of paragraph we are talking lean adults in the overall population, so this is a bigger group as it includes both young adults who would potentially go on to live longer and those who won't. Now we are factoring in the tendency X, from a sub (minor) group, to say that all the lean young adults should comply with tendency X in order to achieve a longer age. Isn't that what option E is saying?

AjiteshArun · Answer

Hi  Namangupta1997 ,

Let's take a statement similar to the author's:

1.   People who become CEOs of big tech companies tend to be Indians with engineering degrees. So Indians can improve their chances of becoming the CEO of a big tech company by getting an engineering degree.  ←  Subgroup  = people who become CEOs of big tech companies,  tendency  = Indians w/ engineering degrees, and  population  = all people in the set.

What's the flaw here? An option equivalent to E would tell us that the problem with the argument is that the entire population doesn't necessarily have the tendency that the subgroup has. But that's not the problem here. In fact, the author isn't even looking at the population as a whole. So "the population as a whole doesn't share the tendency of CEOs of big tech companies to be Indians with engineering degrees" isn't a flaw in an argument that concludes that "Indians can improve their chances of becoming the CEO of a big tech company by getting an engineering degree". The real problem is that the author assumes that an { engineering degree } (for an Indian) leads to { CEO of big tech company }.

Similarly, in this question, the author doesn't say anything about the entire population, so the fact that the population as a whole doesn't necessarily share the tendency of the subgroup to have been lean young adults who gained  ~ 1 pound every year doesn't point to a flaw in the author's reasoning. Even if the population as a whole doesn't necessarily have that tendency, lean young adults may improve their chances of living a long life by gaining  ~ 1 every year.

Raman109 · Answer

People who live unusually long tend to have been lean young adults who went on to gain approximately one pound every year, so lean young adults can improve their chances of living a long life by gaining about a pound every year.

Understanding the argument (leaving the argument on the top to avoid back and forth) -
People who live long (this encompasses practically everyone who lives long) > tend to be lean young adults who gain approx. one pound every year. (there is a correlation. Is there any causation mentioned here? No. Just plain fact and some correlation between two facts). It's kind of some argument such as the car accident rate going down and, at the same time, the liquor sales going down. We are just starting with two plain facts that have a positive correlation. But do we know one caused the other - we don't know yet.

Now, the conclusion followed by the word "so" says that lean young adults, by gaining one pound every year > can improve their chances of living a long life. Now it's saying that "gaining one pound every year" is the cause of improved chances of living. For whom? For the lean young adults.
If our example concludes that - so lower liquor sales lead to lower accident rates. So what are we doing? We have just taken two different facts that were somehow positively correlated and turned that correlation into a cause and effect. This is a classic "causation flaw."

Option Elimination -

(A) gives reasons for the truth of its conclusion that presuppose the truth of that conclusion - A lot to unpeel here. Let's, for the sake of simplicity, ditch the modifiers and look at the core of this option. It says, "The argument gives reasons that presuppose the truth of that conclusion." In plain English, it means that the premises (reasons) assume (presupposes) the conclusion is already true (the truth of the conclusion)." This is called circular reasoning. What is that? Let me share an example - The book is valuable because it's worth a lot of money.
The conclusion is "the book is valuable," and the supporting premise is "it's worth a lot of money." If you look here, the premise is nothing, but the conclusion is stated using different words.

Is the argument given anything like the circular argument? Okay let's see what a circular argument will look like for our argument -
People who live long tend to be lean young adults who gain approximately one pound every year because those who live a long time are generally lean young adults who gain about a pound annually.

Is our conclusion like this circular argument - No. Option A is out. Moreover, from our rethinking, we know it's a causal flaw argument wherein we have just taken two different facts that were somehow positively correlated and turned that correlation into a cause and effect.

(B) proceeds as though a condition that by itself is enough to guarantee a certain result must always be present for that result to be achieved - It says that a condition, i.e., gain one pound every year is sufficient for a certain result (live long) is a necessary condition for that result (live long) to be achieved. This option is confusing us with another common flaw error, i.e., necessary v.s. Sufficient condition.
E.g., Every student who studies diligently will excel in their exams. Here, we have a necessary condition to study diligently, but is studying diligently the only condition to excel in the exam? We may need attitude, good study material, effective strategies, and studying diligently. Studying diligently is not the only reason but the flaw in the argument it assumes it is the sufficient (enough) condition.

Does our argument present any sort of necessary vs sufficiency flaw? No. It's a causation flaw.

(C) assumes without proof that two phenomena that occur together share an underlying cause - Does the argument say that the two phenomena "People who live long (this encompasses practically everyone who lives long)" and "tend to be lean young adults who gain approx. one pound every year" - we have any underlying third cause causing both. No.

(D) concludes that one phenomenon is the cause of another when at most what has been established is an association between them - exactly as we discussed in our rethinking.

(E) fails to recognize that a tendency widely shared by a subgroup within a given population will not necessarily be widely shared by that population as a whole - this means that just because the lean young adults live long by gaining one pound a year is not applicable to the population as a whole (the classic representation flaw). But just hold on - is even the argument extrapolating it to the population as a whole? No. It just falsely states the causality between the positively correlated phenomena.

consistentprep · Answer

Why C is incorrect?  assumes without proof that two phenomena that occur together share an underlying cause”

(C) would fit if the author had said “People who live long and gain weight both do so because of some underlying factor (say, genes).”
But the author didn’t say that; they said “doing the weight gain will cause long life.”
That’s exactly (D)’s description.
So (C) is wrong because it’s about “shared hidden cause,” whereas the argument actually makes a “one causes the other” leap.

Share an underlying cause meaning --> you assume they are both effects of some third hidden factor.
(e.g., “ice cream sales ↑ and drownings ↑, so a hidden cause — hot weather — causes both”).

Why D is correct?  “concludes that one phenomenon is the cause of another when at most what has been established is an association between them”
 Association = Correlation 
Whenever you see:
“Group X has  Trait  A and  Outcome  B” → “So if you do A you’ll get B,”
think “correlation ≠ causation” — GMAT’s go-to trap.

The author observes that long-lived people had a certain weight pattern and assumes replicating that pattern will cause long life.

People who live unusually long tend to have been lean young adults who

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