Pharmacists recently conducted a study with respect to the reasons the

Question

Pharmacists recently conducted a study with respect to the reasons their customers purchased eye drops to soothe eye dryness. Dry eyes were more frequently experienced by customers who wore contact lenses than by customers who did not wear contact lenses. The pharmacists concluded that wearing contact lenses, by itself, can cause contact wearers to have dry eyes.

Which one of the following statements, if true, most seriously undermines the pharmacists' conclusion?

(A) An inherited condition can cause both weak eyesight and dry eyes.

(B) Physical exertion causes dry eyes in many people who wear contact lenses.

(C) Most people who have dry eyes do not wear contact lenses.

(D) Most people who wear contact lenses do not have dry eyes.

(E) Both weak vision and dry eyes cause headaches.

Aj85 · Accepted Answer

This argument employs a common fallacy. That is if two things are happening together one causes other. It assumes that correlation means causation. Choice A correctly identifies the faulty reasoning and identifies the possibility of another condition which may be real cause behind both the problems of poor eyesight and dry eyes.

Rest other choices do not undermine the conclusion. that is they do not directly suggest in any way that contact lenses are not the cause of dry eyes"

Choice B has 2 problems, first it says Physical exertion causes dry eyes in many people who wear contact lenses. But many is not equivalent to 'all' . for proving causation many people is not the appropriate word to use. Even if we remove many then this statement can be interpreted in two ways, physical exertion causes dry eyes and not contact lenses. this does undermines the conclusion. But another interpretation may be wearing contact lenses cause physical exertion which in turn causes dry eyes. This interpretation will support the argument. In any case, the first reason - the usage of uncertain word 'many' itself eliminates this choice.

Choice C - this does not deals with issue itself.

Choice D - again -Most people ? may be most dont have, but still contact lenses can cause dry eyes in some.

Choice E. this does not deals with issue itself

ravikrishna1979 · Answer

Pharmacists recently conducted a study with respect to the reasons their customers purchased eye drops to soothe eye dryness. Dry eyes were more frequently experienced by customers who wore contact lenses than by customers who did not wear contact lenses. The pharmacists concluded that wearing contact lenses, by itself, can cause contact wearers to have dry eyes.

Which one of the following statements, if true, most seriously undermines the pharmacists' conclusion?

(A) An inherited condition can cause both weak eyesight and dry eyes.
Could be weak eyesight means they wear glass or ignore or having laser operated. No where weakens the conclusion 
wearing contact lenses can cause contact wearers to have dry eyes.

(B) Physical exertion causes dry eyes in many people who wear contact lenses.
(C) Most people who have dry eyes do not wear contact lenses.
(D) Most people who wear contact lenses do not have dry eyes. ==> ANSWER
(E) Both weak vision and dry eyes cause headaches

Argument says dry eyes is experienced by people who wore contact lenses.
Lets say the entire dry eyes set is A and contact lenses set is B and normal glasses set is C and no eye sight is D
Set A and B overlaps and Set A and C and Set A and D could overlap
But chance that large unoverlapped set of B could exists

Means lets say
Dry eyes = 10
Contact lenses = 40
NOrmal glasses = 25
No eye sight = 35

Dry eyes coincides with contact lenses is 9 and is equvivalent to 1% of contact lenses. 
so many people with contact lenses are not having dry eyes which is weakening the conclusion that contact lenses causes dry eyes and is clearly mentioned in D

answer should be D

sayantanc2k · Answer

A is alright. This is a typical GMAT-like option:
Conclusion: X causes Y.
Weakening statement: Z causes X and Y. (Thus X does not cause Y - just that they happen together because something else causes both of them).

It is very difficult to pose a solid reason to eliminate D - it is trap, yes - but why is it a trap?
Take a look at the conclusion carefully: Wearing contact lenses CAN cause contact wearers to have dry eyes.

The conclusion does not say  Wearing contact lenses WILL cause contact wearers to have dry eyes . So even if most of the people who wear contact lenses do not have dry eye, that does not weaken the argument, because the argument does not claim that whoever wears or most of them who wear contact lenses WILL have dry eyes. It just implies that there is a chance that if someone wears contact lenses, he/ she will have dry eyes caused by wearing the lenses.

A is indeed the right answer.

ankujgupta · Answer

I am still confused why B is wrong. Isn't it saying that physical exertion rather than contact lenses itself causes dryness.

sayantanc2k · Answer

Option B seems to indicate that the combination of physical exertion and the wearing of contact lenses causes dry eyes. Hence this option in a way strengthens the argument.

Bunuel · Answer

Official Explanation

This argument does not consider that an outside factor may cause some people to have both poor vision and dry eyes. Selection (A) provides an outside factor
for both conditions. It is the correct answer. Selection (D) is tempting, but don’t be misled.

Even if most people who wear contact lenses do not have dry eyes, this does not weaken the argument because it is based on the incidence of dry eyes between people who wear contact lenses and those who do not. Secondly, the author does not argue that wearing contact lenses must cause dry eyes, only that it can cause dry eyes.

Mavisdu1017 · Answer

Hello expert,
The OE of this question is not complete, just addressing D, so need your opinion to B. I think both A and B can weaken the argument with alternative cause, so why B is inferior than A? Thanks in advance.

MartyTargetTestPrep · Answer

Here's the support for the conclusion:

Dry eyes were more frequently experienced by customers who wore contact lenses than by customers who did not wear contact lenses.

So, there is a DIFFERENCE between the frequency of dry eyes in customers who wear contact lenses and and the frequency in customers who do not wear contact lenses, and the conclusion is based on that difference.

Now, here's (B).

(B) Physical exertion causes dry eyes in many people who wear contact lenses.

Notice that (B) doesn't really change what we know. Regardless of what (B) says, it is still the case that dry eyes were more frequently experienced by customers who wore contact lenses than by customers who did not wear contact lenses, and (B) does not provide AN ALTERNATIVE EXPLANATION FOR THE DIFFERENCE between the frequencies of dry eyes. After all, we have no information indicating that customers who did not wear contact lenses do not ALSO experience dry eyes because of physical exertion. In other words, what (B) says could be THE SAME for people who do not wear contact lenses.

Now, let's consider (A).

(A) An inherited condition can cause both weak eyesight and dry eyes.

Notice that (A) does provide an alternative explanation for the difference between the frequencies of dry eyes. It could be that the inherited condition causes both the wearing of contact lenses and dry eyes of people who wear contact lenses, making these people different in both ways from the people who do not wear contact lenses.

We can see why (B) does not weaken the argument and (A) does.

KarishmaB · Answer

When a conclusion says "A causes B," we can weaken it by saying "B causes A" or "C causes both A and B." Don't worry about the "CAN" used in option (A). It does make us doubt our conclusion and that's all we want. We don't need to PROVE the conclusion. We just have to say that it is possible that A doesn't cause B. Hence option (A) works. It says "an inherited condition can cause both" and that is why they appear together often. Not because one causes the other. Option (D) slides into Quant category. Say total 50 people have dry eyes and they buy drops - 10 non contact lens wearers and 40 contact lens wearers. So pharmacists concluded that contact lenses can cause dry eyes. (D) Most people who wear contact lenses do not have dry eyes. Say 200 people wear contact lenses. If only 40 have dry eyes, then most contact lens wearers do not have dry eyes. But it doesn't weaken our conclusion that contact lenses can cause dry eyes. Perhaps they did in the 40 lens wearers. After all, in the rest of the public, only 10 people have dry eyes. That is why option (D) doesn't weaken our conclusion. I discussed this question in a webinar. Check out the video here: https://youtu.be/XCBp62o70Eg

Kartikeya40 · Answer

Option (A) doesn't explain why dry eyes would occur only for people with contact lenses but not for people who use glasses perhaps

MartyMurray · Answer

Notice that the passage doesn't say that people who wear glasses don't experience dry eyes as frequently as people who wear contact lenses. In fact, the passage doesn't say that people who don't wear contact lenses don't experience dry eyes sometimes.

Rather the support for the conclusion is simply "Dry eyes were more frequently experienced by customers who wore contact lenses than by customers who did not wear contact lenses."

So, could be both that people who wear contact lenses experience dry eyes more frequently than all the people who do not wear contact lenses and that people who use glasses experience dry eyes more frequently than all the people who do not use glasses.

So, there's no issue related to people who wear glasses also experiencing dry eyes.

KarishmaB · Answer

Comparison is between 'Contacts' vs 'Others'. 
'Others' includes people with glasses and people with good eyesight.

People with 'contacts' experienced dry eyes more frequently than 'others (glasses + good eyes)'.

(A) An inherited condition can cause both weak eyesight and dry eyes.

This means people with contacts and people with glasses both are likely to have dry eyes more frequently. 
The proportion of dry eyes in 'contacts' group will be higher because everyone has weak eyesight there.
The proportion of dry eyes in 'others' group will be lower because only a fraction has weak eyesight there.

Hence (A) works.

shanalshekhar · Answer

B/c inherited condition can cause both weak eyesight and dry eyes that does not mean wearing contact lenses, by itself, can't cause dry eyes. Both can be the causes. 
 So how is A right?

guddo · Answer

You’re right that (A) does not prove contacts  cannot  cause dry eyes. But the question is “most seriously undermines,” meaning it gives a strong alternative explanation that makes the causal inference unjustified.

The study’s logic is: more dry eyes among contact wearers, so  contacts by themselves  cause dry eyes. (A) shows a plausible  confounder : an inherited condition causes weak eyesight (so people choose contacts) and also causes dry eyes. Then the correlation can be explained without contacts causing anything. That directly attacks the “by itself” part, because dry eyes might be driven by  the condition , not the lenses.

So (A) does not eliminate contacts as a possible cause, but it does make the pharmacists’ conclusion much less supported by their evidence.

Pharmacists recently conducted a study with respect to the reasons the

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