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## #8 - Buyer: As a buyer for a large chain of department stores,

• PowerScore Staff
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#98393
Complete Question Explanation

Parallel Reasoning. The correct answer choice is (B).

This explanation is still in progress. Please post any questions below!
chu___
• Posts: 2
• Joined: Jan 04, 2023
#98717
the pattern of reasoning is

someone will take action X if and only if quality Y is present and quality Z is not present. example A has Y but also has Z so they will not X

i dont understand why A is not the answer. is it just because a snowflake melting is not a "someone"? it follows the reasoning exactly, even more closely than the answer B which is the negative synonym of the reasoning. is there something i am missing that differentiates options A and B in a more concrete way?
Jeff Wren
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#98723
Hi chu,

This question involves conditional reasoning. If you are not familiar with conditional reasoning, you will definitely want to spend a significant time studying it to prepare for the LSAT as it is a fundamental concept tested in both logical reasoning and logic games. It also gives many test takers difficulties until they have studied it well. (I only mention this up front because the rest of this answer discusses these concepts.)

In conditional reasoning, the word "if" is completely different in meaning than the words "only if." The word "if" by itself is a sufficient indicator, while the words "only if" together are necessary indicators.

In your question, you used the words "if and only if." Those words express what is called a biconditional. They do not appear anywhere in this question (either in the stimulus or the answers), so we don't have to worry about them here.

In the stimulus, the buyer states that he or she will buy a garment "only if" it is fashionable and not too expensive for their clientele. This means that the terms after the words "only if" (fashionable) and (not too expensive), are both necessary for the buyer to buy the garment. You could restate the sentence to say "If the buyer buys a garment, then it is fashionable and not too expensive for the clientele."

You could diagram the sentence:

BG -> F + not TEC

(Where BG stands for Buy Garment, F stands for Fashionable, and not TEC stands for not Too Expensive for Clientele.)

This argument uses the contrapositive. (Again if you are unfamiliar with the term, you will definitely want to study this concept).

The contrapositive to the above diagram is:

not F or TEC -> not BG

(which would be read, if it is not Fashionable or it is too expensive for the clientele, then the buyer will not buy the garment.)

The stimulus then states that the evening dress by Peruka is too expensive for the clientele, so the buyer will not buy the garment.

This is a valid argument using the contrapositive.

Answer B perfectly parallels this reasoning and is correct.

Answer A starts off with two sufficient conditions rather than two necessary conditions, so already it is not parallel.

The first sentence of answer A states that if it is in a warm place and not protected by insulation, then a snowflake will melt.

This could be diagrammed,

WP + not PI -> SM

(where WP stands for warm place, not PI stands for not protected by insulation, and SM stands for snowflake will melt.)

We are then told that one of the sufficient conditions doesn't happen (since the snowflake is protected by insulation) and the argument concludes that the necessary condition did not occur. This argument contains an error of reasoning that we call a Mistaken Negation. Just because the sufficient condition fails to occur does not mean that the necessary condition also fails to occur.

Hope this helps.
ertwre
• Posts: 1
• Joined: Mar 26, 2023
#100667
Jeff Wren wrote: Wed Jan 04, 2023 2:51 pm Hi chu,

This question involves conditional reasoning. If you are not familiar with conditional reasoning, you will definitely want to spend a significant time studying it to prepare for the LSAT as it is a fundamental concept tested in both logical reasoning and logic games. It also gives many test takers difficulties until they have studied it well. (I only mention this up front because the rest of this answer discusses these concepts.)

In conditional reasoning, the word "if" is completely different in meaning than the words "only if." The word "if" by itself is a sufficient indicator, while the words "only if" together are necessary indicators.

In your question, you used the words "if and only if." Those words express what is called a biconditional. They do not appear anywhere in this question (either in the stimulus or the answers), so we don't have to worry about them here.

In the stimulus, the buyer states that he or she will buy a garment "only if" it is fashionable and not too expensive for their clientele. This means that the terms after the words "only if" (fashionable) and (not too expensive), are both necessary for the buyer to buy the garment. You could restate the sentence to say "If the buyer buys a garment, then it is fashionable and not too expensive for the clientele."

You could diagram the sentence:

BG -> F + not TEC

(Where BG stands for Buy Garment, F stands for Fashionable, and not TEC stands for not Too Expensive for Clientele.)

This argument uses the contrapositive. (Again if you are unfamiliar with the term, you will definitely want to study this concept).

The contrapositive to the above diagram is:

not F or TEC -> not BG

(which would be read, if it is not Fashionable or it is too expensive for the clientele, then the buyer will not buy the garment.)

The stimulus then states that the evening dress by Peruka is too expensive for the clientele, so the buyer will not buy the garment.

This is a valid argument using the contrapositive.

Answer B perfectly parallels this reasoning and is correct.

Answer A starts off with two sufficient conditions rather than two necessary conditions, so already it is not parallel.

The first sentence of answer A states that if it is in a warm place and not protected by insulation, then a snowflake will melt.

This could be diagrammed,

WP + not PI -> SM

(where WP stands for warm place, not PI stands for not protected by insulation, and SM stands for snowflake will melt.)

We are then told that one of the sufficient conditions doesn't happen (since the snowflake is protected by insulation) and the argument concludes that the necessary condition did not occur. This argument contains an error of reasoning that we call a Mistaken Negation. Just because the sufficient condition fails to occur does not mean that the necessary condition also fails to occur.

Hope this helps.
Can you explain more briefly for me?
Jeff Wren
• PowerScore Staff
• Posts: 124
• Joined: Oct 19, 2022
#100683
Hi ertwre,

I'll try to be a bit briefer, but this is a fairly complex conditional argument, so it does require some detailed explanation.

If you're familiar with conditional reasoning, including how to diagram it, and how to take the contrapositive, then the briefest way that I can explain the question is that the argument in the stimulus has two necessary conditions, one of them fails to occur, then via the contrapositive, the conclusion validly infers that the sufficient condition does not occur. Answer B is the only answer that follows this exactly the same, which is why the reasoning is parallel and it is correct.

In case that wasn't clear enough, I can explain the answer by diagramming the conditional argument in the stimulus and the correct answer choice, and show how they are exactly parallel in form. However, if you are not familiar with conditional reasoning, this explanation probably won't make a lot of sense. (In that case, you should study conditional reasoning as soon as possible).

In the stimulus, the buyer states that he or she will buy a garment "only if" it is fashionable and not too expensive for their clientele. This means that the terms after the words "only if" (fashionable) and (not too expensive), are both necessary for the buyer to buy the garment. You could restate the sentence to say "If the buyer buys a garment, then it is fashionable and not too expensive for the clientele."

You could diagram the sentence:

BG -> F + not TEC

(Where BG stands for Buy Garment, F stands for Fashionable, and not TEC stands for not Too Expensive for Clientele.)

This argument uses the contrapositive. (Again if you are unfamiliar with the term, you will definitely want to study this concept).

The contrapositive to the above diagram is:

not F or TEC -> not BG

(which would be read, if it is not Fashionable or it is too expensive for the clientele, then the buyer will not buy the garment.)

The stimulus then states that the evening dress by Peruka is too expensive for the clientele (TEC), so the buyer will not buy the garment (not BG).

Answer B perfectly parallels this reasoning and is correct.

You could diagram the first sentence of Answer B

PI -> FSE + CS

(where PI means pass inspection, FSE means free of sharp edges and CS means completely sealed)

The contrapositive would be:

Not FSE or not CS -> not PI

(which would be read, if it's not free of sharp edges or not completely sealed, then it will not pass inspection)

The stuffed hippo is not completely sealed (not CS), so it will not pass inspection (not PI).

If you compare the diagrams, you should see that they are exactly parallel in form (i.e. the terms match up exactly).

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