Logical reasoning PrepTest 158 · Section 4 · Question 26

This conclusion doesn't resemble the claim that "C (and not A) must cause B." This conclusion is causal — it implies that good teachers can cause students to excel. But it doesn't rule out another potential cause. So, we can eliminate (A) without even evaluating the premises. (If we did evaluate this answer choice's premises, we'd note that they otherwise resemble the premises in the passage. They establish that "Students -> Excel -> Good Teachers." This answer choice is only wrong because the conclusion doesn't rule out a potential alternative cause, like the student's hard work or intelligence.)

Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Flawed Parallel Reasoning

Passage Summary:
If a dog is a Lab in my neighborhood, then it is well-behaved. If a pet is not trained, then it won't be well-behaved. So, these Labs are well-behaved because of their training, not their breed.

Strategy Overview:

1. Argument or facts? Always argument, so identify premises and conclusions of argument
2. Diagrammable?
1. If yes, diagram out premises and conclusion.
2. Note key identifiable characteristics of argument (How many premises? Quantifiers? Ands/ors? Didn't reverse or negate?). Can also convert specific terms in diagram to As, Bs, Cs, Ds, etc.
1. Eliminate an answer choice as soon as you notice it doesn't possess a key identifiable characteristic the passage possesses
2. Diagram remaining until you find a matching flaw
3. If not, paraphrase what the flaw is
1. Checking to see if a common logical fallacies is committed is very helpful
2. Select answer choice that has the same flaw

Answer Anticipation:
This argument features "if-then" keywords ("every," "if"), which is a strong signal we should diagram the premises and conclusion. We'll diagram the two premises:

1. Lab → Well-Behaved
2. Not Trained -> Not Well-Behaved

However, unlike the premises, the conclusion is a cause-and-effect statement, not an "if-then" statement. Still, we can diagram it:

Conclusion: Training -causes-> Well-Behaved

This isn't the exact flaw we may have predicted when we saw the first two "if-then" premies, but we can wrap our heads around it. From the two premises, we can conclude that every Lab in this neighborhood has been trained ("Lab -> Trained" — take the flipside of the second premise if you need some help seeing how we got there). The conclusion assumes that just because every lab has been trained, the training must have caused the labs to be well-behaved. That's not necessarily true. Especially when every lab also shares another characteristic — they're all labs! Maybe the dog's breed has something to do with their behavior. So, it's a little suspicious that the author assumes it's the training and not the breed that causes the good behavior.

So, we'll look for an answer choice that matches this flaw. In abstract terms, we can have "A" sub in for "Lab," "B" sub in for "well-behaved," and "C" sub in for "training." In that case, the argument asserts that because A -> B -> C, C (and not A) must cause B.

We can also expedite our review of the answer choices if we take a conclusion-out approach. We should compare each conclusion to the abstract version of our conclusion — it should say something like "C (and not A) must cause B." If an answer choice's conclusion doesn't resemble that, we can eliminate it without bothering with the answer choice's premises.

Answer Choice Explanation:
This one matches the abstract version of our argument! We have a premise that parallels the claim that "C (and not A) must cause B." In this answer choice, that's the claim that "it is not icy roads, but carelessness, that causes car crashes when it snows." So, we have "careless" as our "C," "icy roads" as our "A," and "car crashes" as our "B."

The premises establish that "A -> B -> C." The first premise can be translated to "If it snows, then there are more car crashes." The second premise can be translated to "If there are car crashes, then people are careless." Connecting those, we get "Snow -> Car Crashes -> Careless." This matches "A -> B -> C"! Although "snow" and "icy road" aren't identical, that's probably OK. After all, "Lab" and "breed" weren't identical in the passage.

Given the resemblance between the structure of (B)'s bad reasoning and that in the passage, we can safely select (B) and wrap up this question. 

Key Takeaway:
We can also expedite our review of the answer choices if we take a conclusion-out approach. Know what the correct answer choice's conclusion should sound like, and you can avoid reading many premises.

This conclusion resembles the claim that "C (and not A) must cause B." In this answer choice, that's the claim that "it is a sense of rhythm, not the ability to count, that is most responsible for good dancing." So, we have "sense of rhythm" as our "C," "ability to count" as our "A," and "good dancing" as our "B."

However, the premises do not resemble "A -> B -> C." The first premise can be translated to "If one is a musician, then they are a good dancer." The second premise can be translated to "if one is a good dancer, then one is not a mathematician." Connecting those, we get "Musician -> Good Dancer -> Not Mathematician." That looks more like "C -> B -> A." If "sense of rhythm" is implied by "musician," then our C term comes first. And if "ability to count" is implied by "mathematician," then our "A" term comes last.

In other words, this answer choice mixes up the causes. It would have been correct if it said that "the ability to count, and not a sense of rhythm, is most responsible for good dancing."

This conclusion doesn't resemble the claim that "C (and not A) must cause B." This conclusion simply makes a recommendation — it says that you should use butter and not margarine when cooking. The conclusion does not express a cause-and-effect relationship. So, we can eliminate (D) without even evaluating the premises. (If we did evaluate this answer choice's premises, we'd note that they don't resemble the premises in the passage either. In fact, there's only one premise, which says that "Good Cook -> Butter and not Margarine." So, this answer choice does not establish anything like "A -> B -> C" either.)

This conclusion doesn't resemble the claim that "C (and not A) must cause B." This conclusion only eliminates a potential cause (good work). It doesn't assert what caused the students to get As. So, we can eliminate (E) without even evaluating the premises. (If we did evaluate this answer choice's premises, we'd note that they only sort of resemble the premises in the passage. They establish an "if-then" chain, but there's an "and" condition in the "B" spot. They establish that "Students -> A and Not World Problem -> Not Adequate Understanding." This would be another reason to cross off (E).)