Exposure to certain chemicals commonly used in elementary schools as

I think you meant (A) : already have allergy
(B) : exposed to chemicals or become more sensitive

Now for conclusion to be true: If (B) increased then (A) also get increased
We need to find some relationship between (A) and (B)
Option C says: (A) increased not because nurses are NO MORE likely to take more children to hospitals as compared to 10 years ago. It means nurses don't start taking children more now a days. They don't have change in their practice.
Example: If more children visit to hospital then either they are really ill or parents bring them for a check up . Option C removes 2nd possibility ( bring them hospital even they are not ill) .Thus , it strengthens that more children do get ill.

The conclusion is that School children are exposed to an allergic reaction in more number than they are in ten years ago. To validate the consultation we need to confirm that the children didn't have allergic symptoms before sending them to the schools. Option C gives us information that school children with previous allergic reaction were not more.

The answer is C.

The conclusion is that School children are exposed to an allergic reaction in more number than they are in ten years ago. To validate the consultation we need to confirm that the children didn't have allergic symptoms before sending them to the schools. Option C gives us information that school children with previous allergic reaction were not more.

The answer is C.

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I didn't understand how C is the answer. If the Nurses are reporting that proportion has increased from last years, then either the no. of students effected by the chemicals have increased or the nurses are reporting more nos. If the students are less likely to be sent to the nurses now, then how does the proportion increases from last year ?

I am still a bit iffy about B. The entire argument is predicated on this idea that the cleaners or pesticides has been causing an increase in the incidence of nursing visits. It concludes as a result that children have been exposed to greater quantities of chemicals or are more sensitive to them. But, what if it’s something entirely different that’s causing these visits!
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We actually don’t know if there has been an increase in the NUMBER of nursing visits. The passage simply tells us that there has been an increase in the PROPORTION of visits that are for treatment of allergic reaction to the chemicals.

But the bigger issue is one that we referenced in our previous post. The passage has specified that it is the proportion of visits for treatment of “allergic reaction to those chemicals” that has increased. So, we know for sure that allergic reactions to the chemicals, and not something else, are behind the increase. Therefore, (B) does not have to be true for us to conclude that schoolchildren have been exposed to greater quantities of the chemicals or are more sensitive.

I hope that helps!
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Let’s understand the details of the argument.

Premises
1) Exposure to certain chemicals commonly used in elementary schools as cleaners or pesticides causes allergic reactions in some children.
2) Elementary school nurses in Renston report that the proportion of schoolchildren sent to them for treatment of allergic reactions to those chemicals has increased significantly over the past ten years.

Conclusion- Therefore, either Renston's schoolchildren have been exposed to greater quantities of the chemicals, or they are more sensitive to them than schoolchildren were ten years ago.

We need to find an assumption for this argument.

(A) The number of school nurses employed by Renston's elementary schools has not decreased over the past ten years.

This has no relevance to the conclusion of the argument. The conclusion is that, it is either that R’s Schoolchildren have been exposed to greater quantities of chemicals or that they have become more sensitive to chemicals than schoolchildren were ten years ago- Eliminate A

(B) Children who are allergic to the chemicals are no more likely than other children to have allergies to other substances.

The comparison is not between children who are allergic to chemicals and children who are allergic to other substances. Eliminate B

(C) Children who have allergic reactions to the chemicals are not more likely to be sent to a school nurse now than they were ten years ago.

Let’s negate this option to see whether it will impact our conclusion or not. Children who have allergic reactions to the chemicals are more likely to be sent to a school nurse now than they were ten years ago. This means that it is not that Renston's schoolchildren have been exposed to greater quantities of the chemicals, or that they are more sensitive to chemicals than schoolchildren were ten years ago. The negation of the assumption in Option C leads to the negation of the conclusion. Option C confirms what is stated in the conclusion by stating that more school children were not sent to a school nurse now than they were ten years ago. Hence C is our assumption.

(D) The chemicals are not commonly used as cleaners or pesticides in houses and apartment buildings in Renston.

Irrelevant to the argument. Eliminate D

(E) Children attending elementary school do not make up a larger proportion of Renston's population now than they did ten years ago.

This comparison is irrelevant to the argument. Eliminate E.

Vishnupriya
CrackVerbal Prep Team
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GMATNinja EducationAisle what is the meaning of "the proportion of students"? Furthermore, if we had an option stating that the number of students in the school has significantly increased. Would it have a negative impact on the argument?

10 years back:
Total Number of schoolchildren sent to Elementary school nurses = 100
Number of schoolchildren sent to Elementary school nurses for treatment of allergic reactions to those chemicals = 10

So, proportion of schoolchildren sent to Elementary school nurses for treatment of allergic reactions to those chemicals = 1 in 10.

Now:
Total Number of schoolchildren sent to Elementary school nurses = 100
Number of schoolchildren sent to Elementary school nurses for treatment of allergic reactions to those chemicals = 20

So, proportion of schoolchildren sent to Elementary school nurses for treatment of allergic reactions to those chemicals = 1 in 5.

This is meant by increase in proportion of schoolchildren sent to Elementary school nurses for treatment of allergic reactions.

Since the argument are talking about "proportion" (percentage), the absolute "number" does not matter.
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Exposure to certain chemicals commonly used in elementary schools as cleaners or pesticides causes allergic reactions in some children. – Elementary schools commonly use certain chemicals. Some children experience allergic reactions if exposed to such chemicals.

Elementary school nurses in Renston report that the proportion of schoolchildren sent to them for treatment of allergic reactions to those chemicals has increased significantly over the past ten years. – Nurses in elementary schools in a particular town get schoolchildren sent to them for treatment of allergic reactions to those chemicals. The nurses report that the proportion of such schoolchildren they get has increased significantly over the past ten years.

(So, what exactly is the proportion that has gone up?

The proportion of schoolchildren who are sent to the nurses for treatment allergic reactions to those chemicals.

As a proportion of what?

Must be as a proportion of the total number of schoolchildren in elementary schools in Renston. I.e., total number of students sent to the nurses for the treatments as a fraction of the total number of schoolchildren. Something like, say earlier 10% of schoolchildren used to get sent to nurses, and now 30% of schoolchildren get sent.)

Therefore, either Renston’s schoolchildren have been exposed to greater quantities of the chemicals, or they are more sensitive to them than schoolchildren were ten years ago. – The author concludes that one of two things must have happened:

1. The exposure of schoolchildren to the chemicals has gone up
2. Or, the children have become more sensitive to these chemicals

Author’s logic:
Since a higher proportion of children are sent to the nurses for treatment of allergic reactions to the chemicals (basis), either exposure or sensitivity has increased (main point).

Gap(s) in logic:
Maybe a similar proportion of students used to have allergic reactions, but teachers did not send them to nurses as frequently.

- Possibly, they lacked awareness of the symptoms.
- Or maybe they used to prescribe some basic medication themselves, but have since stopped. (Fear of lawsuits, possibly?)

Which of the following is an assumption on which the argument depends?

Framework
We’re looking for something necessary without which the argument wouldn’t make logical sense. The author assumes there can’t be any other reason apart from the one mentioned for why a higher proportion of such children are sent to the nurses.




A. The number of school nurses employed by Renston's elementary schools has not decreased over the past ten years.
Incorrect. What if the number of school nurses employed by the schools has decreased over the past ten years (negation)?
Even then, the argument still remains valid.
In fact, if despite fewer nurses a higher proportion of children were sent for such treatments, perhaps exposure or sensitivity had increased. So, the negation does not break down the logic of the argument.


B. Children who are allergic to the chemicals are no more likely than other children to have allergies to other substances.
Incorrect.Step 1: What does the option mean?
Two groups of children are compared: those who are allergic to the discussed chemicals and those who are not.
What about these groups?
Group 1 is not more likely to be allergic to other things.
In other words, group 1 is equally or less likely to be allergic to other substances.
Now, Is there an assumption in the argument? The argument is about the treatment of, exposure to and sensitivity to certain specific types of chemicals. How children react to other chemicals or substances, and whether the reaction varies are irrelevant to the argument.

C. Children who have allergic reactions to the chemicals are not more likely to be sent to a school nurse now than they were ten years ago.
Correct. Statement: The likelihood of sending such children to a nurse has not increased in the ten years.
This one is in line with our initial understanding. The statement supports the argument.
And, if such children are more likely to be sent to nurses now than they were ten years ago (negation) then the argument breaks down. In that case, to still conclude that the reason must be either exposure or sensitivity doesn’t make sense.
The basis for the conclusion was the fact that a higher proportion of children are sent to the nurses for allergy treatments. And if the chances of sending such children had increased, then increased exposure or sensitivity would not be the reason.


D. The chemicals are not commonly used as cleaners or pesticides in houses and apartment buildings in Renston.
Incorrect.Doesn’t matter. Whether these chemicals are used in houses is irrelevant. The conclusion is pretty broad in this regard. It mentions ‘exposed to greater quantities of the chemicals’. The conclusion does not discuss ‘where’ children get exposed.
So, even if the chemicals are commonly used as cleanness in houses (negation), the argument still remains valid.


E. Children attending elementary school do not make up a larger proportion of Renston's population now than they did ten years ago.
Incorrect. Proportion of the town’s population = # of children at the school / population of the town
Whether this proportion has changed, and if it has, in which direction are immaterial to the argument. Even if the children now make up a larger proportion (negation), the argument is not impacted.

To be honest, this looks very confusing as:

In the question it says: "proportion of schoolchildren sent to nurses for treatment of allergic reactions to those chemicals has increased in 10 years" and option C says: "Children who have allergic reactions to the chemicals are NOT more likely to be sent to a school nurse now than they were ten years ago".

So basically, its contradicting that premise says propoortion has increased and C option says children are not likely to be sent to nurses now.

Could anyone please help GMATNinja or any other expert who reads this first. Thanks a lot!

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Hi Mansha, this is a very common pattern that numerous GMAT questions use. Hence, you should be comfortable with this question type.

Perhaps a simpler example would help.

Argument: A greater percentage of students are getting 100% marks in Mathematics in class 10th now, than was the case 10 years back. Clearly, proficiency in Mathematics has increased in the last 10 years.

What's the assumption? Well, the assumption is that teachers have not become more "lenient" in marking now, than 10 years back.

Think about it. If teachers have become more "lenient" in marking now (than 10 years back), then leniency in marking (and not increased proficiency in Mathematics) explains the reason for greater percentage of students getting 100% marks in Mathematics in class 10th now (than was the case 10 years back).

However, since the argument is saying/concluding that increased proficiency in Mathematics is the reason for greater percentage of students getting 100% marks in Mathematics in class 10th now, then the assumption is that increased leniency in marking is not the reason.
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Thank you for such a prompt response. I get the example you wrote but I am still not convinced that how Option C is correct for the question that I have asked. Could you please explain that as well with respect to the contradictory part that I have mentioned in my post. That would be really helpful. Thanks.

In this argument the premise is: the proportion of schoolchildren sent to school nurses for treatment of allergic reactions to those chemicals has increased significantly over the past ten years.

For the above premise, the argument says that the possible explanations are either of the following:

(X) Renston's schoolchildren have been exposed to greater quantities of the chemicals, or
(Y) they are more sensitive to them than schoolchildren were ten years ago.

But then, for the above premise, a third possible explanation can be:

(Z) Children who have allergic reactions to the chemicals are more likely to be sent to a school nurse now than they were ten years ago (the way in my previous example, teachers were more lenient in marking now than was the case 10 years ago).

However, since the argument is concluding that (X) or (Y) are the possible reasons, the assumption is that (Z) is not the reason (the way in my previous example, the assumption was teachers were not more lenient in marking now than was the case 10 years ago).

This is exactly what C states.
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Can you please help me with one interpretation.
Conclusion is "Therefore, either Renston's schoolchildren have been exposed to greater quantities of the chemicals, or they are more sensitive to them than schoolchildren were ten years ago."

Notice the usage of "the chemical" it means there should be prior mention of this chemicals. This is mentioned in
"certain chemicals commonly used in elementary schools "

So how to eliminate D considering this interpretation

The correct answer is (C).

The argument assumes that the increase in the proportion of schoolchildren sent to school nurses for treatment of allergic reactions to the chemicals is not due to any changes in the way the schools handle the problem. If, for example, the schools are now more likely to send such children to nurses, that would explain the increase in the proportion of children treated for allergies, even if the actual incidence of allergies had remained constant. Answer (C) addresses this assumption by stating that the proportion of children sent to nurses has not changed over the past ten years. Therefore, the argument depends on answer choice (C).

The passage is clearly mentioning that exposure leads to allergic reactions.

And Statement C is saying that

Then how can this be said that it is leading to a separate reason and this statement is correct.

Kindly explain in more simple words or with example if possible.GMATNinjaKarishmaB

I still don’t understand why the answer is not E. Suppose natural rate of children contact with the chemical is same as it was 10 years ago but population is larger. Mathematically it is possible. Can you please explain ??

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Observation: More and more children are being sent to the school nurses because of allergic reactions due to cleaning chemicals over the past ten years.

Conclusion: Either more chemicals are getting used or children are becoming more sensitive.

We are concluding that the cause of the observation is one of these two only. When we say that one of these two is the cause, we are assuming that nothing else is the cause of the observation (that more children are being sent to nurses for allergy).
So we are assuming that nothing else is the cause.

But there is another cause one can think of - what if the teachers are the ones getting more sensitive i.e. what if they are observing children more carefully? What if they are sending children to the nurses upon observing a tiny amount of allergy? What if because of this the children who get an allergic reaction today are more likely to be sent to the nurses than were the children 10 years ago. What if 10 years ago, the teachers did not bother that much until and unless they saw a case of full blown allergy?
That could be another reason why more children are being sent to the nurses now.

Note that the argument doesn't say that more children are getting allergic reactions. It very carefully says that more children are getting sent to the nurses (sneaky GMAT way)

(C) Children who have allergic reactions to the chemicals are not more likely to be sent to a school nurse now than they were ten years ago.

This is an assumption as we discussed above. For our conclusion to hold that only one of those two causes is possible, we are assuming that children who get allergic reactions are not more likely to be sent today than they were 10 years ago.

Answer (C)

Check out this post on assumptions: https://anaprep.com/critical-reasoning- ... ssumption/