In a study, researchers repeatedly measured the thickness of

Question

In a study, researchers repeatedly measured the thickness of a specific artery in each of thousands of volunteers over several years. The researchers found during the study that the artery became thicker more quickly in individuals who lived in cities with significant air pollution. Since thick arterial walls are associated with heart disease, the researchers concluded that exposure to significant urban air pollution contributes to heart disease.

In order to assess the force of the researchers' evidence for their conclusion, it would be most helpful to know whether

A. any of the volunteers whose arteries became thicker during the study lived in areas without urban air pollution

B. the specific artery the researchers examined is fairly typical of arteries in the human body with respect to the thickness of its walls

C. any factors that are more common in urban areas contribute to heart disease without contributing to the thickening of arterial walls

D. any of the volunteers whose arteries were among the thickest at the end of the study had arteries that were among the thickest when the study began

E. any other environmental factors tend, in cities with significant amounts of air pollution, to act to thicken arterial walls more quickly than they do in cities with lower amounts of air pollution

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E

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MartyMurray · Accepted Answer

In a study, researchers repeatedly measured the thickness of a specific artery in each of thousands of volunteers over several years. The researchers found during the study that the artery became thicker more quickly in individuals who lived in cities with significant air pollution. Since thick arterial walls are associated with heart disease, the researchers concluded that exposure to significant urban air pollution contributes to heart disease.

The researchers conclude the following:

exposure to significant urban air pollution contributes to heart disease

The support for that conclusion is the following:

the artery became thicker more quickly in individuals who lived in cities with significant air pollution

and

thick arterial walls are associated with heart disease

We see that the researchers have reasoned that, since something associated with heart disease, "thick arterial walls," is correlated with urban air pollution, urban air pollution contributes to heart disease.

Simply put, the researcher have used a correlation between two events as support for the conclusion that one causes the other.

In order to assess the force of the researchers' evidence for their conclusion, it would be most helpful to know whether

This question is an Evaluate question. So, the correct answer will present a question such that different answers to that question will weaken or strengthen the support for the conclusion provided by the evidence.

A)  any of the volunteers whose arteries became thicker during the study lived in areas without urban air pollution

The evidence that supports the conclusion is a general pattern: "the artery  became thicker more quickly  in individuals who lived in cities with significant air pollution."

Notice that the evidence is not that the artery simply became thicker. It's that it "became thicker more quickly" in individuals in cities with significant air pollution.

Thus, even if some of the volunteers whose arteries became thicker lived in areas without urban air pollution, it would still be true that the artery became thicker  more quickly  in individuals who lived in areas with air pollution.

So, a yes answer to the question presented by this choice does not weaken the support provided by the evidence.

On the other hand, a no answer to this question could seem to strengthen the argument. After all, if none of the volunteers whose arteries became thicker lived in areas without urban air pollution, then we have more reason to believe that urban air pollution causes thickening of arteries.

So, since at least a no answer to the question presented by this choice seems to affect the strength of the argument, let's keep this choice and see whether any other choice is better.

B)  the specific artery the researchers examined is fairly typical of arteries in the human body with respect to the thickness of its walls

Neither a yes nor a no answer to the question presented by this choice affects the strength of the argument.

After all, the support for the conclusion isn't that the specific artery the researchers examined is thicker than other arteries. It's that  the artery's thickness increased faster  in people living in areas with air pollution.

In other words, the evidence doesn't involve simply the thickness of the artery. It involves a change in the thickness, and that change would have the same support for the conclusion regardless of how that artery compares with other arteries.

Eliminate.

C)  any factors that are more common in urban areas contribute to heart disease without contributing to the thickening of arterial walls

Notice that the conclusion is not that "urban areas" contribute to heart disease. It's that "exposure to significant urban air pollution contributes to heart disease."

So, whether other factors common in urban areas contribute to heart disease in other ways is irrelevant.

Another way of seeing that this choice is wrong is that the conclusion is based on the fact that thickening of arterial walls is  one  path or factor associated with to heart disease. That reasoning doesn't depend on it being the case that thickening of arterial walls is the  only  thing that results in heart disease. There could be other factors that cause heart disease in other ways and that fact would not change the fact that one path to heart disease is thickening of arteries.

So, neither a yes answer nor a no answer to the question presented by this choice has any effect on the force of the evidence.

Eliminate.

D)  any of the volunteers whose arteries were among the thickest at the end of the study had arteries that were among the thickest when the study began

The answer to the question presented by this choice has no effect on the force of the evidence. After all, the evidence involves the fact that the arteries became  thicker than they were before , not the fact that they were simply thick.

So. regardless of whose were the thickest, as long as arteries became thicker more quickly in those who lived in areas with air pollution, the argument still works.

Eliminate.

E)  any other environmental factors tend, in cities with significant amounts of air pollution, to act to thicken arterial walls more quickly than they do in cities with lower amounts of air pollution

The answer to the question presented by this choice makes or breaks the force of the evidence that supports the conclusion.

After all, if the answer is "Yes" and there are other factors that act to thicken arterial walls in cities with air pollution, then the correlation between air pollution artery thickening doesn't support the conclusion as well as it would otherwise.

After all, it could be that those other factors, which are correlated with both air pollution and thickening, are actually causing the thickening, rather than the pollution. In other words, some other factor could be causing the thickening, and the pollution could just happen to be present at the same time but not causing the thickening.

On the other hand, if the answer to the question presented by this choice is "No," then we have confirmation that there is not some other factor causing the thickening. So, in that case, we can be more confident that pollution causes the thickening, and in that case, the support provided by the evidence is strong.

So, this choice is looking great.

The only issue is that a no answer to (A) seems to strengthen the argument as well. So, which choice is correct, (A) or (E)?

Here's the thing.

We are not looking for a choice that simply strengthens the case for the conclusion. The question stem asks for information that can be used "to assess  the force of the researchers' evidence  for their conclusion."

So, we can roll with (E) rather than (A) because of the following difference.

A no answer to the question presented by (A) adds some  new evidence  in support of the conclusion. On the other hand, (E) helps to confirm whether the evidence we already have supports the conclusion.

Simply put, (A) is more about new evidence whereas (E) is about the force of the researchers' evidence.

Correct answer:  E

OmerKor · Answer

Hi  MartyMurray ,
Thank you for your elaborate response.

I chose the first answer choice because I could not think of a better answer to that question.
From my perspective (based on what I have learned so far), I believe there is a relation between air pollution   and heart disease  .
However, they did not conclude that  *ONLY*    ->  . 
I encountered both types of questions with these relations, such as Only X -> Y or X -> Y (which implies that  other factor s can lead to Y and is valid for our argument).

There may be additional factors that can increase HD, which is legitimate, (right -_-?)
So, why would any other factors strengthen or weaken the argument? -> As Answer choice E.

MartyMurray · Answer

It'a true that the conclusion could be correct even if other factors cause thickening of arteries and heart disease.

At the same time, the force of the evidence comes from the fact that there is a correlation between degree of thickening and air pollution.

Seeing that correlation, the researchers conclude that air pollution causes the thickening.

So, the issue that (E) brings up is that it could be that, EVEN THOUGH THERE IS A CORRELATION BETWEEN DEGREE OF AIR POLLUTION AND DEGREE OF THICKENING, the conclusion may not be correct because the thickening may be caused by another factor that's associated with air pollution rather than by air pollution.

If a different factor could be causing the thickening, then it could be that air pollution is present when thickening exists but does not cause the thickening. In that case, the evidence is not convincing, and the conclusion is questionable.

So, we can see that knowing whether "any other environmental factors tend, in cities with significant amounts of air pollution, to act to thicken arterial walls more quickly than they do in cities with lower amounts of air pollution" would help with determining whether the conclusion is effectively supported by the evidence.

egmat · Answer

Let me help you tackle this evaluate question systematically. The key to these questions is identifying what assumption the argument relies on and finding the answer choice that tests that assumption.

Argument Structure: 
The researchers present a logical chain:

Observation:  Arteries thickened faster in people living in polluted cities
 Medical fact:  Thick arteries are associated with heart disease
 Conclusion:  Air pollution contributes to heart disease

The Critical Gap: 
The argument assumes that air pollution is  the cause  of the faster artery thickening observed in polluted cities. But correlation doesn't equal causation! What if something else about polluted cities causes the artery thickening?

Evaluating the Answer Choices:

Option A  Whether some people in clean areas also had artery thickening doesn't tell us if pollution caused the effect in polluted cities. This is a distractor.
 Option B  Whether this artery is typical affects generalizability but doesn't address whether pollution actually causes the thickening. The causal claim remains equally strong or weak.
 Option C  This asks about alternative pathways to heart disease, but we need to know about alternative causes for the artery thickening itself.
 Option D  This is about baseline measurements vs. change over time - a study design issue that doesn't address the causal relationship.
 Option E ✓  This directly targets the assumption! If other environmental factors in polluted cities (like stress from traffic, diet differences, less exercise space) also cause artery thickening, then pollution might not be the culprit.

If YES (other factors exist) → Weakens the conclusion significantly
If NO (pollution is the only factor) → Strengthens the conclusion

Why E is Correct: 
Option E is the only choice that helps us determine whether the correlation between pollution and artery thickening represents actual causation. It tests whether alternative explanations exist for the observed pattern.

The Answer:   E

Want to master the systematic framework for tackling all Evaluate questions and learn the advanced patterns that help you spot the correct answer in under 90 seconds? Check out the  complete solution on Neuron by e-GMAT , which includes 3 alternative approaches and shows how this question connects to other CR question types. Access detailed explanations for official questions  here .

Tucky · Answer

MartyMurray  @ KarishmaB  
Although I got this correct, I have a question about (B):

What if the specific artery discussed in the passage is not typical of the human body and is especially susceptible to air pollution, causing it to thicken much more quickly than a normal human artery? 
Wouldn’t this possibility weaken the argument? I understand that choice (E) clearly weakens it, but wouldn’t choice (B) also weaken the argument?

MartyMurray · Answer

Notice how much of a story you created.

(B) is about only whether the "thickness" of the artery's walls is "typical."

You added "especially susceptible to air pollution" and "thicken much more quickly," neither of which is mentioned by (B) or properly inferable if the answer to the question posed by (B) is that the specific artery is not typical.

After all, not fairly typical with respect to  "thickness" does not really mean "thicken."

So, for (B) to weaken the argument, we have to come up with a story that doesn't logically follow from the information in the passage or any possible answer to choice (B).

Borrat · Answer

MartyMurray , Can you help me understand this: multiple factors can cause arterial thickening , and the researcher never claims a true causal claim, just a contribution (in other words lots of causes with varying strengths lead to heart disease) - so why does E hurt the argument? I've used the above reasoning to cross off answer choice E here: https://gmatclub.com/forum/economist-in ... l#p3751116 - E. It fails to address adequately the possibility that a severe economic recession may itself cause more homes to remain on the market unsold. -- also wrong because it doesn't break the causal claim: it says yeah the direction is stronger for recession -> unsold homes (by using " cause more unsold homes ") but it doesn't wreck the (weaker) unsold -> recession causal claim What am i missing here, these seems similar.

guddo · Answer

In a study, researchers repeatedly measured the thickness of a specific artery in each of thousands of volunteers over several years. The researchers found during the study that the artery became thicker more quickly in individuals who lived in cities with significant air pollution. Since thick arterial walls are associated with heart disease, the researchers concluded that exposure to significant urban air pollution contributes to heart disease. 
  
 In order to assess the force of the researchers' evidence for their conclusion, it would be most helpful to know whether

The researchers found that people in polluted cities had faster artery thickening, and they conclude that urban air pollution contributes to heart disease. The key issue is whether air pollution itself caused the faster thickening, or whether some other city-related factor caused it.  So we need to check for an alternative cause  of the artery thickening in polluted cities.

A. any of the volunteers whose arteries became thicker during the study lived in areas without urban air pollution

Wrong. Some thickening outside polluted areas would not weaken the claim. The issue is whether thickening happens more quickly in polluted cities because of pollution.

B. the specific artery the researchers examined is fairly typical of arteries in the human body with respect to the thickness of its walls

Wrong. The argument depends on the observed thickening and its link to heart disease, not on whether this artery is typical of all arteries.

C. any factors that are more common in urban areas contribute to heart disease without contributing to the thickening of arterial walls

Wrong. Factors that do not affect artery thickening do not explain the researchers’ key evidence.

D. any of the volunteers whose arteries were among the thickest at the end of the study had arteries that were among the thickest when the study began

Wrong. The researchers measured how quickly the artery became thicker, so initial thickness is not the central issue.

E. any other environmental factors tend, in cities with significant amounts of air pollution, to act to thicken arterial walls more quickly than they do in cities with lower amounts of air pollution

Correct. This directly tests the causal claim. If another environmental factor in polluted cities causes faster artery thickening, then air pollution may not be the cause. If no such factor exists, the pollution explanation becomes  stronger .

Answer: (E)

MartyMurray · Answer

The information mentioned by (E) can affect the argument in the following way.

The support for the conclusion is a correlation between levels of air pollution and rate of thickening of arterial walls. The researchers, seeing that correlation, conclude that pollution causes arterial thickening.

Now, here's (E):

(E) any other environmental factors tend, in cities with significant amounts of air pollution, to act to thicken arterial walls more quickly than they do in cities with lower amounts of air pollution

So, notice that (E) brings up a possible alternative reason for the correlation: it could be that, rather than that pollution causing the thickening, what's really going on is that other environmental factors that are correlated with but not caused by pollution cause the thickening and pollution has nothing to do with the thickening.

So, determining whether there are such environmental factors could result in calling the conclusion into question, if there are such factors, or increased confidence in the conclusion, if there are not such factors.

Borrat · Answer

so c is wrong because it's providing a completely different cause to the same effect (via an alternative scenario), but we are trying to evaluate a specific chain :  air pollution  -> arteries thicken -> heart disease. - and E hurts the red part?

MartyMurray · Answer

That's basically correct.

Regarding (C), we could put it this way. (C) is incorrect because the conclusion is not that air pollution is the only cause of heart disease. It's that exposure to air pollution "contributes to" heart disease. So, it doesn't matter whether there are other factors that contribute to heart disease. After all, even if there are, exposure to pollution could still contribute to it.

bharathhr · Answer

MartyMurray

What should we evaluate, the main conclusion , or the assumption that the author. what does the question mean when it says , force of the evidence

egmat · Answer

Hi bharathhr,

Good question, because this one really is about the stem, not the answer choices. Marty already flagged this as an  Evaluate  question, and that's the key to your confusion.

"Force of the evidence" = how strongly the given evidence supports the conclusion.  It's not asking you to prove the conclusion true or false. It's asking: does the evidence actually  earn  the conclusion, or is there a gap?

So your "conclusion vs. assumption" split is a bit of a false choice. Look at the pieces here:

Evidence:  in polluted cities, arteries thickened faster (a correlation).
 Conclusion:  air pollution  contributes to  heart disease.
 Assumption (the bridge):  the pollution itself - not some other thing in those cities - is what drove the faster thickening.

When you "assess the force of the evidence," you're testing that  bridge . That's the same thing as testing the assumption. The conclusion and the assumption aren't rival targets - you evaluate the conclusion  by  probing the assumption that links it to the evidence. That's exactly why  E  is right: it asks whether some other factor could be doing the thickening, which is precisely the assumption the evidence rests on.

A tiny stand-in to lock it in

Every morning the rooster crows, then the sun rises. So the rooster's crowing makes the sun rise.

To "assess the force" of that evidence, the most useful thing to know is:  does the sun still rise on days the rooster stays quiet?  Notice you're not attacking the conclusion head-on - you're testing the hidden assumption that the crowing (not the passage of time) is the real cause.

Same move in the artery question: E checks whether the crowing (pollution) is really the cause, or just something present alongside the true cause.

Answer: E

FerociousStorm · Answer

Why is D incorrect ? if someone had thick arterial walls before the study and then they lived in highly polluted city for years and it remained that way, it means pollution didn't affect the condition.

egmat · Answer

Hi FerociousStorm,

I see exactly where your story comes from, and it's a reasonable instinct. But notice that the scenario you built ("thick before → stayed the same despite pollution") isn't actually what (D) says. Let's line up (D) against the evidence.

What the evidence is about:  the artery "became thicker  more quickly " in people living in polluted cities. The support is about the  rate of change  - how fast arteries thickened.

What (D) is about:  whether the people whose arteries were  among the thickest at the end  were also  among the thickest at the start . That's a comparison of  who ranks highest in absolute thickness  - a static, baseline snapshot. It says nothing about how  fast  anyone's arteries grew, and nothing about who lived where.

So (D) never gives you your "pollution didn't affect it" case. Someone can start thick and still thicken quickly; someone can start thin and thicken quickly too. Knowing the start-vs-end  ranking  leaves the rate comparison - the actual evidence - completely untouched. That's why a yes or a no to (D) changes nothing about the force of the argument.

Turn one knob to feel it

Watch how (D) would have to be rewritten to matter:

- As written:  were the thickest-at-end also thickest-at-start?  - about  absolute thickness , irrelevant.
- Rewritten:  did people in polluted cities thicken faster even after accounting for other city factors?  - now it's about  rate , and it bites.

The argument lives entirely in "more quickly." Any choice that only talks about who is  thick  - rather than who  thickened faster  - is off-target. That's the same reason (B) fails, and it's why (E), which asks whether some  other  factor sped up the thickening in polluted cities, is the one that actually tests the causal claim.

Answer: E

guddo · Answer

Not quite. (D) is about  starting thickness , not the rate of thickening.

The study’s evidence is that arteries became thicker  more quickly  in people living in polluted cities. So even if some volunteers already had thick arteries at the beginning, pollution could still have made their arteries thicken faster during the study.

Your example says “it remained that way,” but (D) does not say their arteries remained unchanged. It only says they were among the thickest at both the beginning and the end.

So (D) does not test the real causal issue. (E) does, because it asks whether something other than air pollution might have caused the faster thickening.

MartyMurray · Answer

bharathhr  "the force of the evidence" means something along the lines of "how effectively the evidence supports the conclusion."

So, specifically, in this case, the question is about the degree to which the evidence "the artery became thicker more quickly in individuals who lived in cities with significant air pollution" actually supports the conclusion "exposure to significant urban air pollution contributes to heart disease."

So, information that indicates whether that evidence is meaningful will help in assessing the force of the evidence.

For example, information that shows that there could be in urban areas a cause other than air pollution for the observed arterial thickening would indicate that the fact that arterial thickening occurs more quickly in urban areas doesn't effectively support the conclusion that air pollution contributes to heart disease. After all, in that case, even though people's arteries thicken more quickly in urban areas, air pollution may not be the cause.

So, knowing whether there are in urban areas such other possible causes for arterial thickening would help with assessing the force of the evidence.

In a study, researchers repeatedly measured the thickness of

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