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Exposure to certain chemicals commonly used in elementary schools as 05 Oct 2023, 20:11
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I was confused in A & C.

Why A because. The argument states that the proportion of students visiting them ( nurses ) has increased. It is the collective proportion and not the proportion of student visiting each nurse earlier. If it would have been the proportion of students visiting each nurse. Then decrease in number of nurses would increase the proportion/per nurse.

But after knowing the answer i got to the understanding it was collective proportion.
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Exposure to certain chemicals commonly used in elementary schools as 09 Dec 2023, 08:37
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Vibhatu

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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As you suggest, if the number of elementary school children got bigger, and the rate of exposure to chemicals stayed the same, you'd probably expect more children to be sent to the nurse for treatment.

Notice, however, that (E) doesn't claim that the number of elementary school children stayed the same. Rather, it tells us they do not make up a larger proportion than they did ten years ago. This really isn't necessary to assume. Notice that the number of elementary school children could stay the same even if the proportion changed (depending on the number of non-elementary school people in the town). For this reason, (E) doesn't really relate to the conclusion.

From another angle: notice that the evidence supporting the conclusion doesn't claim that the NUMBER of school children sent to the nurse for treatment increased. Rather, it claims that the "proportion" increased. So even IF the number of elementary school children increased, this wouldn't explain why the proportion being sent to the nurse for treatment increased.

So we wouldn't really need to assume that the number of elementary school children stayed the same (though again, answer choice (E) is talking about the proportion of the town that are elementary school children, not the total number of elementary school children).

Since (E) isn't required to draw the conclusion, it isn't an assumption on which the argument depends, which makes it incorrect.

I hope that helps!
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Exposure to certain chemicals commonly used in elementary schools as 05 Apr 2024, 13:06
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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:

Quote:
(A) The number of school nurses employed by Renston's elementary schools has not decreased over the past ten years.
A change to the number of nurses doesn't impact the number of students sent to see the nurses, so (A) can be eliminated.

Quote:
(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 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.

Quote:
(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.
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.

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

Quote:
 (E) Children attending elementary school do not make up a larger proportion of Renston's population now than they did ten years ago.
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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­
GMATNinja firstly many kudos for your explanations, are always so informative!!

After reading your post I understood the reasoning for choosing (C), but I'd like your guidance to also clearly spot my mistake.

I chose (A) since I thought that the proportion we discuss is number of students with allergic reaction in this chemical to the number of nurses. Given from the question stem that the number of students sent to the hospital rises, based on the first choice, the number of nurses has either increased or remain stable. In the first case, the proportion will increase which answer our question and in the second one there would be no increase in the proportion so it's out of scope.

What am I missing?

Can anyone chip in? GMATCoachBen avigutman Bunuel chetan2u

Thanks in advance ! :blushing:
 ­
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Exposure to certain chemicals commonly used in elementary schools as Updated on: 15 Nov 2024, 00:10
Originally posted by HarshavardhanR on 13 Apr 2024, 21:46.
Last edited by HarshavardhanR on 15 Nov 2024, 00:10, edited 2 times in total.
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Gmatguy007

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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:

Quote:
(A) The number of school nurses employed by Renston's elementary schools has not decreased over the past ten years.
A change to the number of nurses doesn't impact the number of students sent to see the nurses, so (A) can be eliminated.

Quote:
(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 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.

Quote:
(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.
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.

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

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



­
GMATNinja firstly many kudos for your explanations, are always so informative!!

After reading your post I understood the reasoning for choosing (C), but I'd like your guidance to also clearly spot my mistake.

I chose (A) since I thought that the proportion we discuss is number of students with allergic reaction in this chemical to the number of nurses. Given from the question stem that the number of students sent to the hospital rises, based on the first choice, the number of nurses has either increased or remain stable. In the first case, the proportion will increase which answer our question and in the second one there would be no increase in the proportion so it's out of scope.

What am I missing?

Can anyone chip in? GMATCoachBen avigutman Bunuel chetan2u

Thanks in advance ! :blushing:
­
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­Hi Gmatguy007,

Perhaps I can chip in here.

There are a couple of points to discuss.
Quote:
1 - "I chose (A) since I thought that the proportion we discuss is number of students with allergic reaction in this chemical to the number of nurses."
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I am afraid you misunderstood what the given proportion is when you solved this one!

Let's deep dive into the pertinent sentence.

"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."

What the proportion is talking about -> Out of the schoolchildren sent to the nurses overall, how many were sent to the nurses for treatment of allergic reactions to those chemicals.

This is ( Number of children sent to nurses for treatment of allergies related to those chemicals / Number of children sent to nurses for treatment overall (including other reasons like stomach ache) )

This is not ( Number of students with allergic reactions / Number of nurses ). Number of nurses is nowhere in the picture here!

A quick example of proportion: If I say that the proportion of children sent to the principal's office for misbehavior increased, it means ->

(No of children sent to the principal's office for misbehavior / Total number of children (Sent + not sent for the above reason) )

Bottom Line: The argument is not concerned with the proportion you have used - ( Number of students with allergic reactions / Number of nurses ). So, the logic you have used where you are trying to see how this proportion is impacted as a result of choice A - is incorrect.
Quote:
2 - Given from the question stem that the number of students sent to the hospital rises, based on the first choice, the number of nurses has either increased or remain stable.
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I also wanted to focus on the bolded portion above as I feel you may be making an error here in interpreting what is given.

Go through the argument once more - is it really given that the number of students sent to hospitals (for allergy treatment related to those chemicals) increased?

We are only given that the proportion of such students increased.

This is an important concept: An increase in proportion does not necessarily imply an increase in the absolute number.

For example:

10 years ago -> 100 students sent to hospital. 10 for allergies related to these chemicals. Proportion - 10%
Now -> 50 students sent to hospital. Again, 10 for allergies related to these chemicals. Proportion - 20%

The proportion can very well increase without an actual increase in the number. The argument only tells us that a proportion increased. We should be careful not to assume that the number increased too.

Hope this helps!

Cheers,
___
Harsha
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Exposure to certain chemicals commonly used in elementary schools as 14 Apr 2024, 01:44
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HarshaR

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­
GMATNinja firstly many kudos for your explanations, are always so informative!!

After reading your post I understood the reasoning for choosing (C), but I'd like your guidance to also clearly spot my mistake.

I chose (A) since I thought that the proportion we discuss is number of students with allergic reaction in this chemical to the number of nurses. Given from the question stem that the number of students sent to the hospital rises, based on the first choice, the number of nurses has either increased or remain stable. In the first case, the proportion will increase which answer our question and in the second one there would be no increase in the proportion so it's out of scope.

What am I missing?

Can anyone chip in? GMATCoachBen avigutman Bunuel chetan2u

Thanks in advance ! :blushing:
 ­
 
­Hi Gmatguy007,

Perhaps I can chip in here. 

There are a couple of points to discuss.
Quote:
1 - "I chose (A) since I thought that the proportion we discuss is number of students with allergic reaction in this chemical to the number of nurses."
I am afraid you misunderstood what the given proportion is when you solved this one!

Let's deep dive into the pertinent sentence.

"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."

What the proportion is talking about -> Out of the schoolchildren sent to the nurses overall, how many were sent to the nurses for treatment of allergic reactions to those chemicals.

This is ( Number of children sent to nurses for treatment of allergies related to those chemicals / Number of children sent to nurses for treatment overall (including other reasons like stomach ache) )

This is not ( Number of students with allergic reactions / Number of nurses ). Number of nurses is nowhere in the picture here!

A quick example of proportion: If I say that the proportion of children sent to the principal's office for misbehavior increased, it means -> 

(No of children sent to the principal's office for misbehavior / Total number of children (Sent + not sent for the above reason) )

Bottom Line: The argument is not concerned with the proportion you have used - ( Number of students with allergic reactions / Number of nurses ). So, the logic you have used where you are trying to see how this proportion is impacted as a result of choice A - is incorrect.
Quote:
2 - Given from the question stem that the number of students sent to the hospital rises, based on the first choice, the number of nurses has either increased or remain stable.
I also wanted to focus on the bolded portion above as I feel you may be making an error here in interpreting what is given. 

Go through the argument once more - is it really given that the number of students sent to hospitals (for allergy treatment related to those chemicals) increased? 

We are only given that the proportion of such students increased. 

This is an important concept: An increase in proportion does not necessarily imply an increase in the absolute number.

For example:

10 years ago -> 100 students sent to hospital. 10 for allergies related to these chemicals. Proportion - 10%
Now -> 50 students sent to hospital. Again, 10 for allergies related to these chemicals. Proportion - 20%

The proportion can very well increase without an actual increase in the number. The argument only tells us that a proportion increased. We should be careful not to assume that the number increased too.

Hope this helps!

Cheers,
Harsha 
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­Thank you HarshaR for the detailed answer, indeed I made some incorrecrt inferences that changed the whole situation.
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Exposure to certain chemicals commonly used in elementary schools as 16 Jul 2024, 09:01
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Quote:
 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 schoolchildren 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.

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

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

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

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

(E) Children attending elementary school do not make up a larger proportion of Renston's population now than they did ten years ago.
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­Hi, DNS96!

To solve this question, let us deploy IMS's four-step technique.

STEP #1 -> IDENTIFY THE QUESTION TYPE

To identify the question type, we must read the question stem. The stem states, 'Which of the following is an assumption on which the argument depends?' What we have is an assumption question.

Now that the question type is identified, let us proceed to the second step.  

STEP #2 -> DECONSTRUCT THE ARGUMENT

In an assumption question, it is a must to deconstruct the argument by figuring out the conclusion and the premise. Let us therefore read the argument and deconstruct it. 

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.
PREMISE: 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.

Now that the argument is deconstructed, let us proceed to the third step. 

STEP #3 -> FRAME A SHADOW ANSWER

To frame a shadow answer, we need to know what the right answer option is supposed to do. In an assumption question, the correct answer bridges the gap between the conclusion and the premise. There must be something in the conclusion that is missing from the premise. We know the author concludes that Renston's schoolchildren have either been exposed to greater quantities of the chemicals over the past ten years or become more sensitive to the chemicals than schoolchildren were ten years ago. He bases this conclusion on the fact that the proportion of schoolchildren sent to elementary school nurses for treatment of allergic reactions to those chemicals has increased significantly over the past ten years. Let us say in 2023, 100 out of a total of 2000 children were sent to elementary school nurses for treatment of allergic reactions to the chemicals. In 2013, only 10 out of then 1500 children were sent. Clearly, just because 10 children were sent to an elementary school nurses ten years ago does not mean only the 10 sent students were exposed to greater quantities of the chemicals or had sensitivity issues. It is possible that 1000 students had allergic reactions to the chemicals spoken of but only 10 got sent to the nurses. So, for the author's argument to stay on solid ground, he must be assuming that students today are as likely to be sent to a nurse as the students were ten years ago. 

SHADOW ANSWER: Any situation that indicates that students with allergic reactions to the chemicals spoken of are as likely to see elementary school nurses today as students were ten years ago. 

Now that we have a shadow answer, let us proceed to the final step. 

STEP #4 -> ELIMINATE INCORRECT ANSWERS

All answer options that do not match the shadow answer can be eliminated.

(A) The number of school nurses employed by Renston's elementary schools has not decreased over the past ten years. - NOT A MATCH - Not worried about the number of school nurses employed. - ELIMINATE

(B) Children who are allergic to the chemicals are no more likely than other children to have allergies to other substances. - NOT A MATCH - Not worried about allergies to other substances. - ELIMINATE

(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. - MATCHES THE SHADOW ANSWER - 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, it could mean Renston's schoolchildren have not really been exposed to greater quantities of the chemicals than schoolchildren were ten years ago. {Let us say 100 children (out of a total of 2000) actually had allergic reactions after exposure to chemicals this year, and 10 years back, let us say 1000 children (out of a total of 1500) had allergic reactions after exposure to chemicals. But if all 100 were sent this year and only 10 were sent 10 years ago, the author's argument that 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 will fall flat.} What this option states has to be an assumption for the argument to remain on solid ground. - KEEP   

(D) The chemicals are not commonly used as cleaners or pesticides in houses and apartment buildings in Renston. - NOT A MATCH - Not worried about what the chemicals are not commonly used as. - ELIMINATE

(E) Children attending elementary school do not make up a larger proportion of Renston's population now than they did ten years ago. - NOT A MATCH - Not worried about whether or not children attending elementary school make up a larger proportion of Renston's population. - ELIMINATE

Hence, (C) is the correct answer.­
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Exposure to certain chemicals commonly used in elementary schools as 26 Jul 2024, 22:12
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i still dont get why a is wrong.....if 10 nurses looked after 100 kids aka 10 kids per nurse and then 9 of the nurses left then the proportion of schoolchildren sent to the nurse would increase right...?? (100 students per nurse)...?
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Exposure to certain chemicals commonly used in elementary schools as Updated on: 26 Jul 2024, 22:43
Originally posted by bronaugust on 26 Jul 2024, 22:32.
Last edited by bronaugust on 26 Jul 2024, 22:43, edited 1 time in total.
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i still dont get why a is wrong.....if 10 nurses looked after 100 kids aka 10 kids per nurse and then 9 of the nurses left then the proportion of schoolchildren sent to the nurse would increase right...?? (100 students per nurse)...?
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Ask yourself: Does the argument talk of children-nurse ratio or the proportion of schoolchildren sent?
The answer to this question will help you understand why (A) is wrong.
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Exposure to certain chemicals commonly used in elementary schools as 26 Jul 2024, 22:41
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i still dont get why a is wrong.....if 10 nurses looked after 100 kids aka 10 kids per nurse and then 9 of the nurses left then the proportion of schoolchildren sent to the nurse would increase right...?? (100 students per nurse)...?
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­Let us say there were 1000 students in the school 10 years back and let us say there were 10 nurses. Now there are 1500 students and 2 nurses. Let us say the number of students sent to nurses was 10 a decade back. Now it is 16. 10/1000 is less than 16/1500 although the number of students sent to each nurse would be higher now. Clearly, the number of nurses does not play any role in determining the proportion OF SCHOOLCHILDREN sent. The argument DOES NOT say 'proportion of sent schoolchildren per nurse' (or something to that effect). (A) is therefore wrong; the option deals with the number of nurses, and the argument does not concern itself with children-nurse ratio. So even if what is stated in (A) were false, the argument would not fall flat.­
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Exposure to certain chemicals commonly used in elementary schools as 16 May 2025, 02:23
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this was tricky. probably a 605 at least.

a - “This basically states : Same or more nurses; if same nurses ⇒ argument unaffected; if more nurses ⇒ more reports ⇒ weakens.”
b - Whether these children have other allergies is irrelevant. Cross-sensitivities to other substances do not affect the trend the author is trying to explain.
c - If children with reactions became more likely to be taken to the nurse, the higher proportion could stem from heightened reporting, not from greater exposure/sensitivity. Negating this breaks the argument. it presents a malicious variable.
d - The conclusion is about a trend (today vs. ten years ago). Whether the chemicals are or aren’t used in homes now is irrelevant unless we also know the situation then.
e - Talks about children in general, not allergic children → irrelevant
joemama142000
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 schoolchildren 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.

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

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

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

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

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


OG2017, CR635, P536­
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