Gmatguy007 wrote:
GMATNinja wrote:
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.
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(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.
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(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.
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(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 chetan2uThanks in advance !
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.
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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
Enthu about all things GMAT | Exploring the GMAT space | My website: gmatanchor.com
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05 Oct 2023, 20:11
