Q23 - Research indicates that 90 percent

[willaminic]

This question irritates me

I pick D, i really cant see why C is right, the argument is not even about frenquence! Even A seems better than C!

Can anyone explain to me, please. Thank you so much. Love this forum

[giladedelman]

Thanks for the forum love!

Here's an argument for you:

90% of my close friends are American.
Derek Jeter is American, so it's quite likely that he's my friend.

~Wait, what?~

That doesn't make sense! Why? Because there are 300 million Americans out there. I have, I don't know, 20 close friends? So even if 18 of them are American, the fact that Derek Jeter is American doesn't mean he probably fits into that group. It's much more likely that he fits into the 299.999982 million Americans who aren't in my group of friends.

So we would need to know something about what percent of Americans are my friends. If I'm friends with 90% of Americans, then it is actually likely that I'm friends with Derek Jeter.

The same thing is going on with this argument. 90% of insomniacs drink coffee. Okay, but maybe there are 100 insomniacs, and 90 of them drink coffee, but 1,000,000 other people drink coffee, too! Then the fact that Tom drinks coffee wouldn't suggest that he's an insomniac. If all we know is that Tom drinks coffee, we need some information about the frequency of insomniacs among coffee drinkers in order to conclude anything either way.

That's why (C) is right.

(A) is out because the argument does acknowledge this possibility by saying Tom is probably an extreme insomniac, rather than definitely.

(B) is incorrect because the cause is not the issue, the issue is whether or not he's an extreme insomniac.

(D) is incorrect because the argument just says Tom probably fits into a group because he shares a characteristic of that group. It can be okay to do this if your logic is correct; for example, if the argument said "Tom is an extreme insomniac," it would be okay to conclude that "he probably drinks coffee."

(E) is out because the argument doesn't suggest anything about coffee causing insomnia.

Does that clear this up for you?

[willaminic]

Yea, i feel so stupid by making such a mistake. Thank you.

[loveleenzoria]

Hello, would you mind clarifying why D is wrong? Please. I am a bit confused with the explanation you provided.

Thank you.

[gplaya123]

Here is the thing...

This argument involves with conditional logic:

Most of insomniacs tend to consume a lot of coffee.

Insomniac -> Consume a lot of coffee
Tom consumes a lot of coffee.

Therefore he is one.

Wrong , that's mistaken reversal fallacy.

D is wrong because it doesn't apply. It's whole-to-part fallacy but that didn't happen here.

Stupid author qualified this argument by saying that he is quite likely an insomniac, meaning that he left a lot of rooms for doubts...

Now

My question is in regards to the wording of C.

I chose A by the way...

This word "frequency" always throws me off.

C is I guess according up previous post, trying to say that the argument doesn't reveal the size of pool of the insomniacs... this argument is valid or not valid depending on the size of pool?

Someone please help me with the wording... I've seen this kind of answer choices many times...

[wj097]

(E) is out because the argument doesn't suggest anything about coffee causing insomnia.

Does that clear this up for you?

Hey giladedelman,

One question:
I understand that the main flaw committed by the arguer is (C). However, if (E) was reworded to "it assumes that drinking coffee CAN cause insomina" would it be another flaw that it commits? One way the arguer to conclude from an irrelevant premise is to assume a valid assumption, and the reworded version of (E) would make the conclusion valid. Would you say agree on this kind of thinking??

THx

[tommywallach]

Hey Wj,

I like that you're on the lookout for causation/correlation errors, but this argument doesn't actually make one. It goes from a correlation premise (most insomniacs = crazy coffee drinkers) to a correlation conclusion (tom = crazy coffee drinker, so insomniac).

Nowhere does this argument go into causation mode, claiming that one thing causes another. You'll always see the word "cause" or a synonym of it when the LSAT hits that flaw (i.e. "Coffee makes people insomniacs" or "Coffee drinking leads to insomnia" or "Insomnia is a symptom of coffee drinking".)

Hope that helps!

-t

[WaltGrace1983]

Hey Wj,

I like that you're on the lookout for causation/correlation errors, but this argument doesn't actually make one. It goes from a correlation premise (most insomniacs = crazy coffee drinkers) to a correlation conclusion (tom = crazy coffee drinker, so insomniac).

Nowhere does this argument go into causation mode, claiming that one thing causes another. You'll always see the word "cause" or a synonym of it when the LSAT hits that flaw (i.e. "Coffee makes people insomniacs" or "Coffee drinking leads to insomnia" or "Insomnia is a symptom of coffee drinking".)

Hope that helps!

-t

However, even though this is not exactly causal language the argument does give some conditional language, am I right? While insomnia might not CAUSE drinking large amounts of coffee, having insomnia is SUFFICIENT for concluding that one probably drinks a lot of coffee, right? (By the way, I am trying to be very conscious and careful of not saying that insomnia is sufficient for drinking lots of coffee but, instead, saying that insomnia is sufficient for concluding that one most likely drinks a lot of coffee).

I just want to make sure I am thinking about this correctly.

As for the other question, I'll try and help out!

C is I guess according up previous post, trying to say that the argument doesn't reveal the size of pool of the insomniacs... this argument is valid or not valid depending on the size of pool?

Someone please help me with the wording... I've seen this kind of answer choices many times...

Here is how I thought about the problem...

Insomniac → Likely to "Consume large amounts of coffee"
Tom "Consumes large amounts of coffee"
→
Tom = Insomniac

Again, I am going to try and be careful here because we aren't given any real sufficient condition/necessary condition, as we just know that most insomniacs drink lots of coffee and not all insomniacs drink lots of coffee.

Anyway, the problem is that we don't know how many people who drink large amounts of coffee, relative to the whole population, are insomniacs. If we say that there are 100 insomniacs in America, we know that ~90 of them are going to consume large amounts of coffee. What is the problem here, then? The problem is that so many Americans (wayyyyyy more than only 90 people) consume large amounts of coffee.

The conclusion, therefore, doesn't really follow from the premises because we don't know if the insomniacs who drink large amounts of coffee make up a sizable population or not. Look at this argument...

"90% of the 1,000,000 insomniacs in America drink large amounts of coffee. There are about 910,000 coffee drinkers in America. Since Tom drinks a lot of coffee, it is quite likely that he is an insomniac"

Now compare it to this argument...

"90% of the 1,000,000 insomniacs in America drink large amounts of coffee. Since Tom drinks a lot of coffee, it is quite likely that he is an insomniac"

The difference is that, in the first argument, we have a general understanding of how many people are BOTH insomniacs AND drink large amounts of coffee vs. BOTH not insomniacs AND drink large amounts of coffee. In other words, we have a basis for concluding that Tom, because he drinks a lot of coffee, is fairly likely to be an insomniac.

I hope that makes sense!

[WaltGrace1983]

So (E) is wrong for two reasons, right? The first would be the word "always" - it only concludes that it is "quite likely." the second would be that it discusses causation, when there is nothing causal (but perhaps conditional) about this stimulus. Right?

[christine.defenbaugh]

So (E) is wrong for two reasons, right? The first would be the word "always" - it only concludes that it is "quite likely." the second would be that it discusses causation, when there is nothing causal (but perhaps conditional) about this stimulus. Right?

Exactly it, WaltGrace1983!

The conclusion does not make any sort of 'always' claim, nor does it conclude a thing about causation specifically.

What we do have in the argument is a lot of stuff about correlations. So if you noticed the correlations, and immediately thought 'well, we must be dealing with causation/correlation' without actually checking for that structure, then (E) would be tempting.

Great work!

[aliciaq]

Hi, I understand how C points out the mistaken reversal, but if the conclusion said, Tom is an extreme insomniac, so it is quite likely that he drinks a lot of coffee. Would this be an inference error about an individual from a group or would it be correct to infer this?

[cyt5015]

Hi, I understand how C points out the mistaken reversal, but if the conclusion said, Tom is an extreme insomniac, so it is quite likely that he drinks a lot of coffee. Would this be an inference error about an individual from a group or would it be correct to infer this?

I think it is correct to infer, because the conclusion uses "quite likely" rather than "surely".
If I say: Rich people likes to donate their money to charity. Tom is rich, clearly, he likes to donate his money to charity. Then, the flaw would be that infer one specific individual from evidence that describes only the characteristics of a class of people. "like to donate money" is a typical or representative feature of rich people, not a necessary feature to all rich people.

[cyt5015]

I think answer A may strengthen the argument, and my reasoning is below:
"10 percent of people who drink a lot of coffee who are not extreme insomniacs" implies 90 percent of people who drink a lot of coffee are extreme insomniacs. Tom drinks a lot of coffee, then it is reasonable to conclude that it is quite likely that he is an extreme insomniac.
Tom is possible to be among the 10% of people who are not extreme insomniacs, but more likely to be among the 90% of people who are insomniacs.
Is my reasoning valid? Thank you.

[donghai819]

It would be interesting to think this question in these two ways

93 percent people who run a lot are becoming vulnerable to knee injury. Since Tom runs a lot, it is quite likely that he is vulnerable to knee injury. (E would be the correct answer)

and,

93 percent people who run a lot are becoming vulnerable to knee injury. Since Tom's knee often gets injured, he probably runs a lot.

[krishna.kilambi]

Suppose if the question is changed in the following way,

90 percent of extreme insomniacs drink large amounts of coffee , Ted is an extreme insomniac so he likely to drink a large amount of coffee.

Is it a valid conclusion ?