Bunuel wrote:
Electrician Magazine surveyed 1,000 electricians who took an advanced certification exam. Of these 1,000 candidates 500 passed the exam and 500 failed. The magazine asked the electricians how many hours they had studied for the exam. It was found that those who passed had studied on average 50 hours, and those who failed had studied on average 20 hours. The magazine concluded that the more hours one studies, the more likely he is to pass.
Which of the following, if true, would most strengthen the conclusion of the magazine?
A. Some of the electricians in the survey actually studied more than 100 hours.
B. Many of those surveyed thought the exam was unnecessary and did not reflect on their ability as electricians.
C. The electricians in the survey all took the exam shortly after reaching five years of experience as an electrician.
D. Many of the electricians who passed had completed a course in electronics covering some of the topics also included in the syllabus of the certification exam.
E. Majority of the electricians who failed had college degrees in a variety of fields not related to electrical subjects.
1000 people took an exam. 500 passed. 500 failed.
It was found that the 500 who passed had studied on avg 50 hrs while 500 who failed had studied on avg 20 hrs.
Conclusion: The more hours you put in, the more likely you are to pass.
We need to strengthen this. Note that there could be many reasons why the 500 who passed actually did pass. We only checked for one characteristic and that was the number of hours they put in. What if the 500 who passed had an avg experience of 10 yrs compared with an avg experience of 2 yrs of those who did not pass? What if the 500 who passed had already acquired some related certifications and hence knew the material much better? What if the 500 who passed had college degrees in the field of Electricals? Any one of these could be the differentiating factor. We only checked for one factor (number of hrs) and concluded based on that. We can strengthen that number of hours was responsible by showing that other possible factors were not responsible.
C. The electricians in the survey all took the exam shortly after reaching five years of experience as an electrician.
Option (C) says that they had the same experience. So it says that a difference in their experience level was not responsible. So it increases the likelihood that 'number of hrs put in' was the factor responsible. Note that it just increases the probability but that is all we need from a strengthener - an increased probability.
A. Some of the electricians in the survey actually studied more than 100 hours.
We are talking about averages in our argument. Even if some people studied a lot (we don't know whether they passed or failed), it doesn't impact our conclusion.
B. Many of those surveyed thought the exam was unnecessary and did not reflect on their ability as electricians.
What they thought about the importance of the exam is irrelevant.
D. Many of the electricians who passed had completed a course in electronics covering some of the topics also included in the syllabus of the certification exam.
If anything, it weakens the conclusion. It links 'passing' with another factor - 'other courses in electronics.' But it doesn't tell us that those who failed had not completed such courses so the information is limited. In any case, we can be sure that it doesn't strengthen.
E. Majority of the electricians who failed had college degrees in a variety of fields not related to electrical subjects.
Same as option (D). If anything, it weakens the conclusion. It links 'failing' with another factor - non electrical degree. But it doesn't say that those who passed had electrical degrees. But in any case, we know that it doesn't strengthen.
Answer (C)
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17 Aug 2015, 11:11
57%
(01:32)
wrong 
