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#24966
Complete Question Explanation

Parallel Flaw—SN. The correct answer choice is (B)

As with any Parallel Flaw question, the first step to answering this question is to understand the flaw in the stimulus. Here, the stimulus contains conditional reasoning. It states that if a child is to develop healthy bones, his or her diet must include sufficient calcium. We can diagram this relationship as follows:
  • Sufficient ..... ..... ..... ..... ..... Necessary

    Develop healthy bones ..... :arrow: ..... Diet includes sufficient calcium
The author then draws the conclusion that children who did not develop healthy bones, did not have a diet with sufficient calcium. This is a mistaken negation, as the author negated both parts of the conditional relationship, but did not reverse the sufficient and necessary conditions. The correct answer choice will make the same mistake. Additionally, the correct answer choice must contain conditional reasoning, and we can quickly eliminate any answer choice that does not contain it. While many students are intimidated by Parallel Reasoning or Parallel Flaw questions, it can actually be fairly easy to narrow down answer choices. As further explained below, in this question, we can quickly eliminate three answer choices simply because they do not contain any conditional reasoning. Even if someone didn’t understand exactly how the conditional relationship is structured, just recognizing the type of reasoning used can help narrow down the answer choices.

Answer choice (A): This is a valid argument. It states that in order for bread to have a firm crust, it must be baked at the right temperature. The conclusion drawn in the second sentence is a valid contrapositive of the initial relationship. Since the argument is valid, it cannot be the correct answer choice in a Parallel Flaw question.

Answer choice (B): This is the correct answer choice. The argument contains conditional reasoning, with a mistaken negation just as we saw in the stimulus. The relationship here is as follows:
  • Sufficient ..... ..... ..... ..... Necessary

    Cake tastes good ..... :arrow: ..... Use the right amount of flour
The conclusion negates that relationship by stating that if the cake does not taste good, the right amount of flour was not used. The structure of the argument matches the stimulus, so it is correct.

Answer choice (C): Structurally, this stimulus does not contain a conditional relationship and a mistaken negation. There is no “if…then” relationship presented. Since the correct answer must be structurally identical to the stimulus, this cannot be the correct answer choice.

Answer choice (D): As in answer choice (C), this answer choice does not contain a conditional relationship, and thus cannot be the correct answer choice.

Answer choice (E): Again, as in answer choices (C) and (D), this answer choice does not contain a conditional relationship and is incorrect.
 sgrimsdale
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#18662
Hi there,

I am really struggling with this question. I think I may be diagramming incorrectly. Can someone explain why B is the correct answer?

Thanks!

Sarah
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 Dave Killoran
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#18664
Hi Sarah,

It's may be the wording in the stimulus that's throwing you off or the wording in the correct answer since both have peculiarities, so let's look at both parts.

The argument in the stimulus is a Mistaken Negation:

  • Premise: Healthy Bones :arrow: Sufficient Calcium

    Conclusion: Healthy Bones :arrow: Sufficient Calcium
The tricky part above is the phrase "sufficient calcium," because that makes you think calcium is a sufficient condition. But, that's not the idea here. What they mean is a certain amount of calcium (and if they had said just that, this would have been easier to parse). So, if you have healthy bones, you need a certain amount of calcium in your diet, and that means the calcium is the necessary condition.

Ok, now that we have a Mistaken Negation in the stimulus, we see a Parallel Flaw question, so we need the same thing in the correct answer.

Answer choice (B) also contains a Mistaken Negation:

  • Premise: Taste Good :arrow: Right Amount of Flour

    Conclusion: Taste Good :arrow: Right Amount of Flour
Here, it's the first sentence that creates the issue, via the phrase "in order to." "In order to" typically immediately precedes the sufficient condition, so in this case "Taste good" is the sufficient condition, making "Right Amount of Flour" the necessary condition. the conclusion then negates both terms, making this a Mistaken Negation.

Please let me know if this helps. Thanks!
 sgrimsdale
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#18666
That is very helpful, thank you! I had missed "in order to" and diagrammed that answer choice backwards, hence my confusion.
 otubu21
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#47982
Hello. I am still not seeing how A and B are any different. I was left with those 2 and selected A.
 Alex Bodaken
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#48042
otubu21,

Thanks for the question. Let me see if I can help.

Answer choice (A) states: "If bread is to have a firm crust, it must be baked at the right temperature. It therefore follows that bread that is not baked at the right temperature will not have a firm crust." We could diagram the first sentence as such:

Bread firm crust :arrow: Baked right temp

And the second sentence as:

Baked right temp :arrow: Bread firm crust

This is valid reasoning, as the second sentence (the conclusion) is a valid contrapositive of the reasoning laid out in the first sentence (the terms are flipped and negated). Because this is valid reasoning, it cannot be our answer choice to a parallel flaw question (after all, our correct answer must contain flawed reasoning).

Answer choice (B) reads: "A cake must contain the right amount of flour in order to taste good. It therefore follows that cakes that do not taste good do not contain the right amount of flour." We could diagram the first sentence as:

Cake tastes good :arrow: Right amount of flour

And the second sentence as:

Cake tastes good :arrow: Right amount of flour

This is a mistaken negation: the terms have been negated but not flipped, as would need to be done for a valid contrapositive. This is the same mistake made in the stimulus, which makes it our credited answer.

Hope that helps!
Alex
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 rye211
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#86873
Diagrammed the question right but missed the conclusion on answer choice B. I'm not catching the sufficient and necessary indicators here. I chose A after finishing diagramming all and not finding my mistaken negation conclusion.
 Robert Carroll
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#86896
rye,

The indicators in answer choice (B) are similar to those in the stimulus. In the stimulus, "is to" indicates the sufficient condition - in answer choice (B), "in order to" does the same. In the stimulus, "must" indicates the necessary condition, which is identical to the corresponding indicator in answer choice (B). The indicators for the conclusion of the stimulus and the conclusion of answer choice (B) look similar to me as well. "therefore follows that" would be a conclusion indicator.

Because you diagrammed the stimulus correctly, just rely on those indicators you found there! Because answer choice (B) has almost the same indicators, it is possible to match them pretty closely to each other. Note that the order of the conditions in the premise of answer choice (B) differs from the order in the stimulus, but seeing where the word "must" applies (sufficient calcium in the stimulus, right amount of flour in answer choice (B)) can help untangle this superficial difference.

Robert Carroll

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