Exposure to certain chemicals commonly used in elementary schools as

The author concludes that one of two things has happened over the past ten years: either 1) Renston’s schoolchildren have been exposed to greater quantities of the chemicals, or 2) they are more sensitive to the chemicals than schoolchildren were ten years ago. How does the author arrive at this conclusion?

• We are given that exposure to cleaners and pesticides commonly used in schools can cause allergic reactions in some children.
• Over the past ten years, the proportion of schoolchildren sent to school nurses for allergic reactions to THOSE chemicals has increased significantly.

The author states two possible explanations for this increase, but are those the only options? The author's explanation will only hold up if one of the following is assumed:


A change to the number of nurses doesn't impact the number of students sent to see the nurses, so (A) can be eliminated.


We are not concerned with allergies to other substances. Regardless of whether children allergic to the chemicals are more likely to have allergies to other substances, we still need to explain why more students are now sent to the nurses because of reactions to THOSE chemicals. The two theories in the conclusion are only meant to explain the increase in the number of schoolchildren sent to the nurses because of THOSE chemicals, so choice (B) is irrelevant.


According to the argument, the increase in the proportion of schoolchildren sent to the elementary school nurses is due to either greater exposure to the chemicals or a greater sensitivity to the chemicals. But what if 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? Maybe the amount and severity of the allergic reactions was the same ten years ago but students were simply less likely to be sent to the nurse back then. Maybe ten years ago the teachers simply let the suffering students remain in class with watery eyes and running noses (for example).

That could explain the increase in the proportion of schoolchildren sent to the elementary school nurses, even if students' exposure and sensitivity to the chemicals has not changed. In order for the argument to hold, the author must assume that 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. Choice (C) looks good.


Perhaps the cleaners ARE commonly used in houses and apartments, but we don't care about WHERE the students were exposed to the chemicals. If exposure has increased, whether at school or at home, then the author's argument would be valid. The author does not say that exposure has increased AT THE SCHOOLS, so choice (D) can be eliminated.


We are trying to explain an increase in the PROPORTION of students sent to the nurses, not an increase in the TOTAL NUMBER of students sent to the nurses. Thus, an increase in the number of students or the proportion of the population attending elementary schools does not matter. We need to explain the increase in the PROPORTION sent to the nurses for those allergic reactions. Choice (E) is not a required assumption and can be eliminated.

Choice (C) is the best answer.
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Question Stem
Which of the following is an assumption on which the argument depends?
Assumption Question- Ask the question - what is required so that the conclusion is true. Also use the negation test on last 2 option choices.

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

Pre-thinking
More children became aware of the symptoms and reported the same. So they were sent to the nurses.

Answer Choices

A. The number of school nurses employed by Renston’s elementary schools has not decreased over the past ten years.
INCORRECT ANSWER - This answer could have been correct if the argument did not mention "PROPORTION". Even if the nurses reduced, the proportion calculation would still remain the same -
\(\frac{No of students sent}{Total no of students}\)

B. Children who are allergic to the chemicals are no more likely than other children to have allergies to other substances.
INCORRECT ANSWER - "other substances" is outside the scope of 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 ANSWER - If the chance that children are sent to the nurse is same, then the conclusion is true.

Negation Test - 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 - So this statement rules out both the options in the conclusion. So this is the CORRECT ANSWER.

D. The chemicals are not commonly used as cleaners or pesticides in houses and apartment buildings in Renston.
INCORRECT ANSWER - If not used commonly then the chemical may not be a reason. It weakens the conclusion.

E. Children attending elementary school do not make up a larger proportion of Renston’s population now than they did ten years ago.
INCORRECT ANSWER - "larger proportion of Renston’s population" - this does not matter. The argument is not talking about this but the proportion of students sent to nurses.

IMO 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'- is the assumption so try to negate this statement and negation will hurt the conclusion.

'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'
In this case more children are sent to the nurse therefore the incidences are reported more and allergic reactions has not increased significantly.

close call between A and C here.

Negating A means that as the number of nurses has decreased,even though the number of children sent remains the same,children seen/nurse has increased.

Negating C means it is more likely that children will be sent to the nurses now than earlier.

C seems closer to the conclusion here. The number of nurses hasn't been discussed in the stem.

Hence C preferred.

Hi Mun23.
My pleasure to help.

Premise: exposure to chemical ==> allergic reactions
Premise: the proportion of schoolchildren sent to them for treatment of allergic reactions increase
Conclusion: more children exposed to greater quantities of the chemicals, or they are more sensitive

Assumption: proportion = children who got allergy and were brought to hospital / Total children.
KEY is "children actually were brought to hospital". If they got allergy and NOT went to hospital, they are not counted.

A. The number of school nurses employed by Renston’s elementary schools has not decreased over the past ten years.
Wrong. Out of scope.

B. Children who are allergic to the chemicals are no more likely than other children to have allergies to other substances.
Wrong. Out of scope

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. This is the assumption above.

D. The chemicals are not commonly used as cleaners or pesticides in houses and apartment buildings in Renston.
Wrong. SHELL GAME. "are NOT used in houses & apartment" DOES NOT MEAN "are used in school". What if the chemical are not commonly used in both school & houses.==> We cannot conclude children exposed to greater quantities of the chemicals.

E. Children attending elementary school do not make up a larger proportion of Renston’s population now than they did ten years ago.
Wrong. We cannot conclude the number of children increased or decreased, because the proportion also depends on the total population that may increase or decrease.

Hope it helps a little bit.

Took a lot of time to decide between C und E.
We have a sound argument here, so don't look for GAP in this case, we need a DEFENDER (see CR Bible) here, which eliminates a possible WEAKENER.

1) The argument says there are 2 possible reasons - a weakener could be a 3rd possible reason, which we eliminate.
2) Let's talk about proportions, relevant proportion here is a # of children sent with allergic reactions / # of school children


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. That could be our 3rd reason and is actually a good weakener. So sliminating this one would DEFEND our argument.

E. Children attending elementary school do not make up a larger proportion of Renston’s population now than they did ten years ago --> This one talks about the wrong proportion - so, it doen't weaken the argument. We need a proportion children with allergie / children and not children / population of the city.

I can see your confusion, but you have to be careful about the exact language in the question. This question is about "certain chemicals", but answer choice B is talking about chemical other than those "certain chemicals". It's what we would call "out of scope" of the argument because it's not talking about the same chemicals.

Your rationale about other causes is perfectly suited to C. It eliminates the possibility that people are just more likely to run to the nurse when experiencing a reaction.

KW
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Hi there,


Argument Deconstructed

- Background (Fact): some chemicals used in elementary schools cause allergic reactions in children.
- Premise (Fact): Nurses in one particular school say that in the past 10 years, a bigger proportion of school children have been sent to them for treatment of these specific allergic reactions.
- Conclusion (Opinion): Only two explanations are possible: 1-Either children have been exposed to greater quantities of the chemical or 2-they are more sensitive than schoolchildren were ten years ago.



Negation Test
I´ll try to explain this question with the Negation Test. In other words, I will negate each answer choice to see whether the new, negated version hurts the argument or not. The one that does, will be our correct answer.

This tactic is based on the fact that an assumption is a hidden or unstated new premise for the argument. If you address a premise, this will strenghten the argument. If you address a premise but also revert its meaning (Negation Test), this will weaken the argument.


A. The number of school nurses employed by Renston’s elementary schools HAS DECREASED over the past ten years.
So what? Irrelevant

B. Children who are allergic to the chemicals are MORE LIKELY than other children to have allergies to other substances.
So what? This doesn´t actually explain the rise in the proportion of children sent to the nurses in the past 10 years.

C. 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.
Waaaaait a minute. This would crash the argument. The author stated that there could be only 2 reasons for the rise in number of children sent to nurses (exposure to greater quantities or more sensitiveness). If we negate this AC, this would imply that there is another (a third) possible cause.

D. The chemicals ARE commonly used as cleaners or pesticides in houses and apartment buildings in Renston.
So what? Completely irrelevant.

E. Children attending elementary school DO MAKE UP a larger proportion of Renston’s population now than they did ten years ago.
So what? This one tries to confuse you with the concept of proportions. Anyway, negating this answer doesn´t hurt the argument.

The passage does not state that the number of students reporting PER NURSE has increased - it states that the PROPORTION OF STUDENTS reporting has increased. Therefore it does not matter, how many nurses are there. Hence A is wrong.

Hi Calvados,

In this particular question, option C invalidates the original conclusion by providing an alternate reason.

Conclusion: 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.

Negate option C: 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 negated statement means that the children are not sent to nurses because of increased exposure to chemicals or increased sensitiveness but are just more likely to be sent to nurses now than 10 years ago when they exhibited allergic reactions.

Thanks chiragmishra93 for the explanation!

According to the argument, the increase in the proportion of schoolchildren sent to the elementary school nurses is due to either greater exposure to the chemicals or a greater sensitivity to the chemicals. But what if 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? That could explain the increase in the proportion of schoolchildren sent to the elementary school nurses, even if students' exposure and sensitivity to the chemicals has not changed.

Thus, in order for the argument to hold, the author must assume that 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. Choice (C) is the correct answer.
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I think the answer is C. The author of the statement has concluded that the children have either been exposed to a higher level of chemicals or are more sensitive than children were ten years ago but is assuming that there is not an alternative reason why children are going to the nurse. C is the only answer that supports that conclusion since if children were more likely to be sent to the nurse than before, it could be something other high exposure or sensitivity.

Summary - Nurses assume children are more exposed to chemicals, or more sensitive than children were 10 years ago as the # of cases has increased significantly.
Assumption - The likelihood of children sent to the nurse after being exposed is the same as it was 10 years ago. In other words, nothing has changed.




The number of nurses has decreased over the past ten years. Great, but it has no impact on the conclusion. OUT


I won't even try an opposite test on this option, as it's irrelevant. OUT!



Children who have allergic reactions to the chemicals are MORE LIKELY to be sent to a school nurse than they were ten years ago. If that's the case, it completely destroys the argument's conclusion that students are either more sensitive now, or are more exposed to the chemicals.

KEEP!



This option is similar to in other countries blah blah blah happens. We are only concerned with the use of the pesticides and cleaners at the school.
TO make this assumption work, we would also have to assume that even though the students were exposed at home, they were sent to the school nurse instead of going to the doctor at a hospital etc.

OUT!



This is irrelevant. OUT!


C is the answer IMO.
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The argument concludes by stating that the increase in proportion of school children sent to elementary school nurses for treatment of allergic reactions to chemicals might be either because the students have been exposed to greater quantities of the chemicals, or that they are more sensitive to chemicals than schoolchildren were ten years ago. The argument is hence, assuming that these are the only 2 possible reasons for the increased proportion. Thus, we need to find an answer choice that eliminates any alternative reasons. What would cause the conclusion to break down ? - Pointing out an alternative reason. Possible alternatives : 1) What if the number of students has increased over the past ten years ? Then the proportion could be higher without children being more sensitive or being exposed to these chemicals on a greater scale. 2) What if earlier also the magnitude of the reaction was similar but children were not sent to schools then ( ten years ago) probably because it was felt that a treatment is not required, however over the period of ten years more children are being sent to nurses.

(A) The number of school nurses employed by Renston's elementary schools has not decreased over the past ten years. - The number of nurses is irrelevant; the argument is talking about the proportion of reported cases here.
(B) Children who are allergic to the chemicals are no more likely than other children to have allergies to other substances. - argument talks about allergies to only chemicals and not other substances.
(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. - Yes, negate this: 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 would naturally lead in an increased proportion of students being sent to nurses and this breaks down the conclusion that there can only be two possible reasons.
(D) The chemicals are not commonly used as cleaners or pesticides in houses and apartment buildings in Renston. - This is irrelevant.
(E) Children attending elementary school do not make up a larger proportion of Renston's population now than they did ten years ago. - The comparison and argument is limited to elementary school children and is nowhere related to the rest of the population.

C is correct.

- The premise is talking about this ratio \(Total # of students sent / Total # of Students\).
- This has increased. The possible reasons for this are
i) Exposure to greater quantities of chemicals
ii) They are more sensitive to chemicals now than 10 years before

Now lets look at the options. REMEMBER, we need to find an assumption

(A) The number of school nurses employed by Renston's elementary schools has not decreased over the past ten years. -->This doesn't affect the ratio in any way. It is not necessary for the argument to hold true. Hence INCORRECT

(B) Children who are allergic to the chemicals are no more likely than other children to have allergies to other substances. --> we are not concerned about substances. Hence INCORRECT

(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. --> Bingo! Lets negate this option. If children are more likely to be sent to school nurse now than they were ten years ago. Then this gives us alternate reason for the increase and weakens the conclusion. Hence CORRECT

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

(E) Children attending elementary school do not make up a larger proportion of Renston's population now than they did ten years ago. --> This option doesn't affect the ratio the premise is talking about in anyway. INCORRECT
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Summary - Nurses assume children are more exposed to chemicals, or more sensitive than children were 10 years ago as the # of cases has increased significantly.
Assumption - The likelihood of children sent to the nurse after being exposed is the same as it was 10 years ago. In other words, nothing has changed.

How is this the assumption. The arguments states lementary school nurses in Renston report that the proportion of schoolchildren sent to them for treatment of allergic reactions to those chemicals has increased significantlyover the past ten years. It says proportion of school children sent for treatment has increases significantly. Can you please explain?

I think you are confusing "proportion of schoolchildren" (includes those with and those without allergic reactions) with "proportion of children who have allergic reactions."

Yes, "the proportion of schoolchildren sent to nurses for treatment of allergic reactions to those chemicals has increased significantly over the past ten years." I.e. maybe ten years ago only about 10% of school children were sent to the nurse for the allergic reactions, and nowadays about 20% of school children are sent.

But that does NOT say anything about the proportion of children who have allergic reactions. For example, maybe ten years ago, only 50% of children with allergic reactions were sent to the nurse. If THAT proportion has remained relatively constant, then the conclusion makes sense.

But what if nowadays nearly 100% of children with allergic reactions are sent to the nurse? That could explain the overall increase in the proportion of schoolchildren being sent to the nurse.

I hope that helps!
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sayantanc2k GMATNinja,

I understand option A is clarified above and why it is wrong but I am not convinced yet. Proportion has increased that can also mean that nurses are same in count and students count has increased and so they are more cases as compared to past.

In this sentence, "Elementary school nurses in Renston" refers to a single group representing all nurses. The phrase "schoolchildren sent to them" does not express a ratio of students to nurses. It's more like saying "schoolchildren sent to any nurse" or "schoolchildren sent to any nurse's office."

• If we were told that the size of this group (the number of nurses) had tripled, from 10 to 30, this would have absolutely no impact on the proportion of students being sent to this group.
• If we were told that the size of this group had shrunk, from 10 to 5, this would also have absolutely no impact on the proportion of students being sent to this group.

However, if 20% of schoolchildren were sent to a nurse this year (regardless of the number of nurses) and only 5% of schoolchildren were sent to a nurse office 10 years ago (again, regardless of how many nurses were available), then we would say that the proportion of schoolchildren sent to a nurse has increased over the past ten years.

That's why we eliminate choice (A). The argument tries to explain why the proportion of children being sent to a nurse has gone up. The ratio of nurses to students is irrelevant.

I hope this clarifies further!
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