Q14 - Expert: A group of researchers

[ohthatpatrick]

Question Type:
Flaw

Stimulus Breakdown:
Conclusion: Perfectly omnidirectional antennas do NOT need to be symmetrical and have a fractal structure.
Evidence: Researchers developed an antenna that is symmetrical and has a fractal structure. But it was NOT perfectly omnidirectional.

Answer Anticipation:
Huh? You got the wrong counterexample there, Bub. If you're concluding that "perfectly omnidirectional antennas do NOT need to have X and Z", then you need to provide us with an example of something that IS perfectly omni antenna bus is NOT "X and Z". Instead, you provided us with an example of something that IS "X and Z" but is NOT perfectly omni. This is the same argument as saying, "US Presidents do not have to be white males. After all, Bob is a white male, and he's not President."

Correct Answer:
D

Answer Choice Analysis:
(A) We definitely don't need a definition of "fractal" to see the problem with this reasoning.

(B) Author's virtually NEVER contradict themselves, yet this answer shows up a ton. (The usual language is that the author "introduces claims that are inconsistent with each other").

(C) This is the famous "Unproven vs. Untrue" flaw, but THIS argument is not that. This argument is simply our author giving us a backwards counterexample.

(D) Somehow, yes, this works! If the original claim the author is fighting were "if X and Z, then perfectly omni", then the author's counterexample would have worked perfectly. He would be saying: "Nuh-uh! Look at this thing that IS "X and Z" but IS NOT perfectly omni."

(E) Extreme = "only". Although the author says that something performs better below 250 than above 250, that doesn't mean that the author fails to recognize the existence of being exactly 250. It was just an arbitrary way of expressing a statistic. If I say that "people who make more than $100k tend to be happier than people who make less than $20k", I'm not taking for granted that those are the only two possible income brackets.

Takeaway/Pattern: This is definitely a tough answer choice to dig out, since the Conditional Logic Flaw it describes is normally manifested differently. But since the counterexample the author presented was "backwards", we should still be receptive to this type of wording.

#officialexplanation

[jennifer]

I was able to get the correct answer, but i upon review I do not understand answer choice D. Can someone pleAse translate answer choice D into simple language and tell me what is the suff and necessary in the stimulus. Thank you

[bbirdwell]

(D) is shorthand for "there is a necessary/sufficient flaw," which means "the logic (the arrow, if you symbolize it) goes the wrong way."

This is an answer choice that is actually predictable after reading the stimulus and noting the characteristic nec/suff structure. The LSAT does this over and over and over again.

Take the first sentence:
If the antennae works equally at all frequencies, then it MUST be symmetrical AND fractal.

Language of necessity (must, depends, requires, prerequisite, etc.) always indicates a necessary condition (the right side of the arrow).

This, here we have:
work well at all freq --> sym & fractal

Then the conclusion:
An antennae that is symmetrical AND fractal does NOT work equally well at all frequencies.

Translation:
sym & fractal --> NOT work well

Notice how this is an INCORRECT contrapositive of the original statement. In other words, it's what we can refer to as a "necessary sufficient flaw," in a ballpark sense.

In (D), the condition that we know is necessary is "sym & fractal." The author inappropriately interprets this as the sufficient condition in the next situation.

[shirando21]

(D) is shorthand for "there is a necessary/sufficient flaw," which means "the logic (the arrow, if you symbolize it) goes the wrong way."

This is an answer choice that is actually predictable after reading the stimulus and noting the characteristic nec/suff structure. The LSAT does this over and over and over again.

Take the first sentence:
If the antennae works equally at all frequencies, then it MUST be symmetrical AND fractal.

Language of necessity (must, depends, requires, prerequisite, etc.) always indicates a necessary condition (the right side of the arrow).

This, here we have:
work well at all freq --> sym & fractal

Then the conclusion:
An antennae that is symmetrical AND fractal does NOT work equally well at all frequencies.

Translation:
sym & fractal --> NOT work well

Notice how this is an INCORRECT contrapositive of the original statement. In other words, it's what we can refer to as a "necessary sufficient flaw," in a ballpark sense.

In (D), the condition that we know is necessary is "sym & fractal." The author inappropriately interprets this as the sufficient condition in the next situation.

C is confusing me, can you explain the difference btw C and D?

Also, usually we pick an answer like D in cases like:

A-->B+C,

B+C-->A

but this one is

A-->B+C

B+C-->-A
we can use this expression as well?

[amthorp]

I am also confused by how C and D are different. Is it because C says "on the grounds that there is insufficient evidence" implying that the Expert should have asserted in writing that "there is insufficient evidence", which he didn't do?

The Expert's claim implies that he believes there is sufficient evidence to refute the researchers' claim.

[tommywallach]

Hey Amthorp,

No, the flaw described in (C) is a common one on the LSAT, but it doesn't appear in this argument. I'll give you an example of it:

Some people think Steve robbed the liquor store, but he couldn't have. Nobody saw him do it.

The error in this argument is that it's concluding that a claim is false (i.e. Steve robbed the liquor store) merely because there isn't any evidence that it's true (i.e. nobody saw him do it). But that doesn't mean Steve didn't do it! Maybe nobody was around!

This argument doesn't make an error that is anything like that. It's not saying that the researchers are wrong (good antennas have to be symmetrical and have a fractal structure) merely because there's not enough evidence to prove them right. It's saying the researchers are wrong because there's a piece of evidence that seems to contradict what they said.

Of course, it turns out it doesn't contradict; that's just the difference between a necessary and a sufficient condition. To make it more obvious:

My amazing theory: To be happy, you must have food and water.

Your response: But Steve has food and water, and he's unhappy. You're amazing theory sucks.

See the problem? I didn't say food and water was all you needed to be happy (Sufficient condition). I said they were necessary in order to be happy.

Hope that helps!

-t

[sch6les]

The researchers say: equally well at all frequencies => symmetrical + fractal.

The expert misinterperts the researchers as saying: symmeterical + fractal => equally well at all frequencies.

And since the experts' result is: symmeterical + fractal => ~equally well at all frequencies, he concludes the researchers are incorrect. But he is in fact incorrect, because he originally switched around the necessary and sufficient conditions of the researchers' claim. This is what (D) states.

[tzyc]

I'm confused by the words in (B)...could you provide an example which shows this situation?

Thank you

[BarryM800]

I got this question right and was able to rationalize it based on the logic, but it's the diagraming that got me confused. The researchers' claim is: All frequencies → Symmetrical and fractal. The expert's premise is: Symmetrical and fractal → NOT All frequencies; CP: All frequencies → NOT Symmetrical and fractal. Wouldn't this contradict the researchers' original claim by fulfilling the sufficient condition, while denying the necessary condition? Where did it go wrong? Thanks!

[Laura Damone]

Great question, Barry!

The issue here is that you mistook a series of fulfilled and denied conditions for an actual conditional statement. The argument opens with a conditional statement:

Works equally well --> Symmetrical + Fractal

Then, it introduces the new antenna, which fulfills the two necessary conditions: it is both symmetrical and fractal. It also denies the sufficient condition: it works better at some frequencies than others.

But all that doesn't imply that whenever the necessary conditions are fulfilled it guarantees the denial of the sufficient. In other words, it doesn't describe a conditional relationship. It just tells us that in this particular case, an antenna fulfilled both necessaries and denied the sufficient.

Since it's not a conditional statement, you can't contrapose it. And since you can't contrapose it, it doesn't fulfill the sufficient while denying the necessary.

As you clearly reasoned since you answered the question correctly, fulfilling the necessaries while denying the sufficient is consistent with any conditional statement. If I said to you, for example, that improving one's LSAT score depends on hard work and a good course of study, it's still possible that someone could work hard, have a good course of study, but not improve their LSAT score.

When I diagram, I use a circled abbreviation for a fulfilled condition. It's an important part of my diagramming repertoire, as questions frequently hinge on recognizing the difference between fulfilled conditions and conditional statements! Since I'm typing here, I'll put things I would have circled in parentheses. When an argument includes the refutation of a conditional statement, I represent that by drawing the conditional and crossing out the arrow.

EWAF --> SS + FS
(SS)
(FS)
- (EWAF)
-----------------------
EWAF --/-> SS + FS

Hope this helps!

[HarshS283]

I am a little confused by this question. The argument says that for an antenna to work equally well at all frequencies, it must have A and B. And, then later claims that though the antenna has A and B, it works better at frequencies below 250 megahertz than at above. However, even if the antenna works better below 250 megahertz, it can be that at above 250 megahertz it still works well. I thought the correct answer would be that exposes this shift in language. I couldn't find any, so I chose B. However, I knew B was wrong.