#20 - Martha's friend, who is very knowledgeable about

[GLMDYP]

Hi Powerscore!
For this question, I chose answer (D), and I don't think (C) is quite right since the annoying "some" there. Can you please tell me how (C) is right and (D) is wrong?
Thanks!

[David Boyle]

Hi Powerscore!
For this question, I chose answer (D), and I don't think (C) is quite right since the annoying "some" there. Can you please tell me how (C) is right and (D) is wrong?
Thanks!

Hello,

When LSAC says something is right, it's usually right, by the way. --"Some" may annoying to some ( . . . ) people, but it's quite useful, as it accounts for a multitude of possible numbers ("one", "many", "all", etc.). The stimulus basically says, "Some daisies are chrysanthemums, some chrysanthemums are edible, so some daisies are edible." This chimes with the bad reasoning in C, where, "some sisters are on debate team, some debaters are poor students, therefore some sisters are poor students".
(You chose answer D, which has "most", but "most" isn't in the stimulus.)

David

[wwarui]

Hi Dave,

September 1998 Logical Reasoning Section II
Question: 20

Please explain the stimulus and the answer to this question. I haven't been able to figure out the correct answer even after redoing it without a timer.
Thanks.

[Robert Carroll]

wwarui,

Rephrase what the stimulus is saying to make the flaw more apparent:

Some daisies are chrysanthemums

Some chrysanthemums are edible and palatable

So, some daisies are edible and palatable

We don't know that daisies and edible, palatable chrysanthemums overlap. Say there are 10 kinds of chrysanthemums, 2 of which are daisies. This leaves 8 kinds of chrysanthemums that are not daisies. Say that 2 of these 8 are the only edible, palatable chrysanthemums. Then there is no overlap between daisies and edible, palatable chrysanthemums - they are totally different groups. This is the flaw in the reasoning.

Answer choices:

A: Jeanne is a member of the chorus, and the chorus is renowned. The flaw here is twofold: saying that if the whole is renowned, something must be true of the part (Jeanne), and saying that Jeanne is excellent just because the chorus is renowned (we don't have any reason to think there must be a connection between excellent singing and being renowned). This is not the flaw we are looking for.

B: All members of the group are avid readers, and Rolfe is a member of the group. Thus, he is an avid reader. This is valid! So it's not the correct answer.

C: Say the debate team has 10 members, and 2 of those are Noriko's sisters. Of the remaining 8, 2 are poor students. We don't know if the groups overlap, so this exhibits the same flaw as the stimulus and is the correct answer.

D: Most of Leon's friends are good swimmers, and all good swimmers are quite strong. Those friends are therefore quite strong. So it's likely that some of them (most of them is still some!) are quite strong. This is not the correct answer.

E: The issue with this answer is not what is in the stimulus, where two groups that did not need to overlap were assumed to overlap (that was the flaw). Here, instead, there is new information in the conclusion: some of Teresa's colleagues are good writers. We only know that many have written books, and most of those books are on good writing. We don't know that they ARE good writers, only that they have written on the subject. This is a flaw, but not the one we need.

Robert

[wwarui]

Hi Robert:

This is one of the hardest areas for me. I am going to redo the lesson on this topic until I can start rephrasing properly. I am very grateful. Thank you.

[ericj_williams]

wwarui,

Rephrase what the stimulus is saying to make the flaw more apparent:

Some daisies are chrysanthemums

Some chrysanthemums are edible and palatable

So, some daisies are edible and palatable

We don't know that daisies and edible, palatable chrysanthemums overlap. Say there are 10 kinds of chrysanthemums, 2 of which are daisies. This leaves 8 kinds of chrysanthemums that are not daisies. Say that 2 of these 8 are the only edible, palatable chrysanthemums. Then there is no overlap between daisies and edible, palatable chrysanthemums - they are totally different groups. This is the flaw in the reasoning.

Answer choices:

A: Jeanne is a member of the chorus, and the chorus is renowned. The flaw here is twofold: saying that if the whole is renowned, something must be true of the part (Jeanne), and saying that Jeanne is excellent just because the chorus is renowned (we don't have any reason to think there must be a connection between excellent singing and being renowned). This is not the flaw we are looking for.

B: All members of the group are avid readers, and Rolfe is a member of the group. Thus, he is an avid reader. This is valid! So it's not the correct answer.

C: Say the debate team has 10 members, and 2 of those are Noriko's sisters. Of the remaining 8, 2 are poor students. We don't know if the groups overlap, so this exhibits the same flaw as the stimulus and is the correct answer.

D: Most of Leon's friends are good swimmers, and all good swimmers are quite strong. Those friends are therefore quite strong. So it's likely that some of them (most of them is still some!) are quite strong. This is not the correct answer.

E: The issue with this answer is not what is in the stimulus, where two groups that did not need to overlap were assumed to overlap (that was the flaw). Here, instead, there is new information in the conclusion: some of Teresa's colleagues are good writers. We only know that many have written books, and most of those books are on good writing. We don't know that they ARE good writers, only that they have written on the subject. This is a flaw, but not the one we need.

Robert

I also think E is wrong because it goes from some to most, unlike the stim and C which go from some to some.

[Jeremy Press]

Hi Eric,

I think it would be better to stick with the reasons Robert gave for eliminating answer choice E. Here's an argument that would be very close to the argument in the stimulus and would contain the same kind of flaw:

Some dogs are furry. Most friendly, furry animals are trainable. Thus, some dogs are trainable.

Does the "most" render the second premise a little different than the premise in the stimulus? It does, so of course I'd prefer to see a complete match (with the term "some" in it). But is the flaw really different than the one in the stimulus or in answer choice C? No. It's the same flaw. In the stimulus, I don't know that the chrysanthemum daisies are in the category of edible chrysanthemums, and so I can't conclude that any daisies are palatable. In my hypothetical argument, I don't know that the furry dogs are in the category of friendly furry animals, and so I can't say that any of them are trainable. Same flaw.

Long story short, always keep an eye on the "big picture" in Parallel Flaw questions, which is to identify the reason a particular premise (or premises) don't automatically lead to a particular conclusion. That's the most important thing to identify in the stimulus and each answer choice.