Critical Reasoning

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.

This is an assumption question, it is also a cause and effect question. The effect that has been observed and cannot be contradicted is that more children are going to the school nurse. Now the speculation is about the cause. The conclusion says that the cause is either "children have been exposed to greater quantities of the chemicals, or they are more sensitive to them than school children were ten yrs ago."

So, in order for that to be the cause, we are assuming that we do not have a more logical or compelling cause. If this were a weaken question you would get another, better cause. Since this is an assumption we want to rule out other causes. Choice C mentions a possible alternative cause and then assures us that it is not present. "Children who have allergic reactions to the chemicals are not more likely to be sent to a school nurse now than they were 10 yrs ago." Ruling out this alternative cause is necessary for the two causes mention to be the ONLY causes.

For assumption questions in general...

Mitch has mentioned the Assumption Negation Technique. Here are a couple of other ways to see assumption questions. Please use the technique or techniques that work best for you!

If there is a clear logical gap then you can certainly jump on that one. Here is an article that discusses critical reasoning and specifically how to spot those "gaps in logic" that gughanbose mentioned. https://www.beatthegmat.com/mba/2013/02/ ... ng-ability


Let me also take slightly different angle. This next article talks about doing assumption questions where you DO NOT spot a gap. On assumptions you will not always see the gap. If you do not then you can approach the question using the "infomercial technique" described here.
https://www.beatthegmat.com/mba/2012/06/ ... -an-expert

Don't over think it. Remember the essence is that you are just looking for the answer that is required by the argument!

Dear Guruny,
How the negating the correct answer choice invalidates the conclusion? I didnt understand that. Here Negating the correct answer is strengthening the conclusion rite?? Can you explain it further more. Actually I want to understand the idea.

Thanks
Divya

Dear David,
Thank you for the explanation. I understood that infomercial test. Also i want to know whether negation can be applied here or not?

Thanks
Divya