Divya Ann Chacko wrote: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.
Premise:
The proportion of schoolchildren SENT TO THE NURSE for treatment of allergic reactions to certain chemicals has increased significantly over the past ten years.
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.
The conclusion suggests two possible explanations for the increase in the proportion of students sent to the nurse:
1) Greater chemical exposure.
2) Greater chemical sensitivity.
The assumption is that there is NO OTHER POSSIBLE EXPLANATION.
Apply the NEGATiON TEST.
When the correct answer choice is negated, the conclusion will be invalidated.
Answer choice
C, negated:
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 negation of
C offers an alternate explanation for the increase in the proportion of students sent to the nurse:
Over the past ten years, students with allergic reactions have become MORE LIKELY TO BE SENT TO A SCHOOL NURSE -- invalidating the conclusion that the increase is due to greater chemical exposure or greater chemical sensitivity.
The correct answer is
C.
Reasons to eliminate:
A:
The number of school NURSES has no bearing on the proportion of STUDENTS sent to the nurse.
Eliminate A.
B:
The passage is about allergic reactions to CERTAIN CHEMICALS.
Allergic reactions to OTHER SUBSTANCES is beyond the scope of the argument.
Eliminate B.
D:
The negation of D implies that the students are being exposed to the chemicals at home, possibly STRENGTHENING the conclusion that greater exposure is to blame for the increase in the proportion of students sent to the nurse.
Since the negation of the correct answer choice must INVALIDATE the conclusion, eliminate D.
E:
The composition of the entire population has no bearing on the proportion of students sent to the nurse.
Eliminate E.
Last edited by
GMATGuruNY on Wed May 13, 2015 3:07 am, edited 1 time in total.
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