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Parallel Flaw—FL. The correct answer choice is (E)
Although this type of formal logic appears less frequently on the LSAT today than it has in the past, some questions still require you to understand it. The supplemental materials for Lesson 8, accessible via the Online Student Center, provide an extensive Virtual Module on formal logic, along with a downloadable chapter on the same topic.
This stimulus involves a problem with chain reasoning. The stimulus states that most auto mechanics have extensive experience, and since most auto mechanics with extensive experience understand electronic circuits, most auto mechanics understand electronic circuits. We can abstract the idea as follows: Because most people belonging to category A have trait B, and most people with trait B understand C, most A’s understand C. This chain does not work, and it is easier to explain with numbers. Let’s say there are 100 auto mechanics. The term “most” indicates more than half, so at least 51 auto mechanics have extensive experience. Of those 51, most understand electronic circuits, so at least 26 understand electronic circuits. The author draws the conclusion that most auto mechanics, or at least 51 auto mechanics, understand electronic circuits. As we could see from breaking down the argument, we do not know that at least 51 auto mechanics understand electronic circuits. The correct answer choice must parallel this structure. Remember that as soon as an answer choice is not parallel to the stimulus, we can eliminate it as incorrect.
We can “speed up” this process of elimination by recognizing that the correct answer choice must contain an argument with the following structure:
- Premise: A most B
Premise: B most C
Conclusion: A most C
Answer choice (A): This answer choice does not use terms that indicate “most,” such as “a majority:” While the term “most” is not required in the correct answer choice, the idea of a majority certainly is required as it is essential to understand the error made. Therefore, you should eliminate this answer choice after a very quick read of the answer choice.
Answer choice (B): Unlike answer choice (A), this answer choice uses the term “most.” The beginning of the answer choice matches the structure of the stimulus. Most birds in the area are migratory (have trait A). Most migratory birds leave by November (most of those with trait A do B). However, the conclusion of the argument varies, and states that “few” birds remain. Just because “most” birds leave, doesn’t mean that only “few” are left.
Answer choice (C): Though this answer choice includes the concept of “most,” it does not include a faulty chain of logic. It even contains some conditional ideas in the conclusion by stating that most drivers who are not interested in driving fast do not buy sports cars.
Answer choice (D): In order to really understand this answer choice, it is easiest to abstract it out to see if the argument is the same as in the stimulus. Most nature photographers find portrait photography boring. We can abstract that as most As find B. Most portrait photographers especially enjoy photographing dignitaries. Since portrait photographers are a new group, we would abstract that as most Cs enjoy D. This is not the same sort of chain relationship we had in the stimulus, and thus the argument is not parallel.
Answer choice (E): This is the correct answer choice. Most A (snow removal companies) run B (lawn-care companies in the summer). Most B hire C (more workers in the summer). Therefore Most A hire C. Abstracting the answer choice we find this answer choice matches the stimulus, and makes the same error in using the term “most.”