PT43.S3.Q21 - each of the many people who participated

jmac800

http://7sage.com/lsat_explanations/lsat-43-section-3-question-21/

I am not sure if this is the right place to post question. But the video explanation was missing something to me.

So you have

Spring Cleanup
|---------------------------------|---------------------------------|
Certificate
<----------------------------------------------------------->

Not Active in the art circle (some but some can mean all as well)
<------------>




Now there may be some kind of implicit assumption that Spring cleanup too place at the same time as the art fair. And some people at the spring cleanup are not active in town's artistics circles. So the assumption here is that if you did not go to the art fair, then you are not active in the town's artistic circles. And if you are active in artistic circles, you did go to the art's fair. It is also (seems) to be assuming that art fair and spring cleanup are mutually exclusive. We aren't really sure.

The answer choice makes no sense, we actually know nothing about people who ARE ACTIVE in the art circles. Which makes D impossible as an answer choice. You simply cannot conclude NOTHING about it. It Could Be True, but this is a MUST be true question.

ENTJ

D? Are you implying that D is the correct answer choice that you're contesting? You mean B right?

ENTJ

PTSC: People that participated in the town's spring clean up.
RCRC: Received a community recognition certificate
TAC: Town's artistic circle.

Each of the many people that participated in the town's annual spring clean up received a community recognition certificate. (PTSC-->RCRC)

At least some spring clean up participants are not active in the town's artistic circle.
(PTSCsome/TAC)

What's the inference? There's a common variable in "PTSC".
So, RCRCsome/TAC or /TACsomeRCRC

What does answer choice B say? Not all of those who receive community recognition certificates are active in the town's artistic circles. Not all implies what? Some.

RCRCsome/TAC.

The answer would also be right if you said: "Not all of those who are active in the town's artistic circles receive community recognition certificates." (/TACsomeRCRC) Why? Because some statements are reversible.

Hope that makes sense.

jmac800

I am sorry, I meant B. I was implying B cannot be the correct answer, it was a typo above.

D was the answer that I saw as being correct (but is incorrect according to the answer key)

The reason I thought D was correct is because if you look at my map above

All people who get a certificate participate in the cleanup. However, I know it is wrong because it is a Could Be True Statement. As there could be other people who get certificates and who do not participate in cleanup. So when I came to this answer I first chose D as the better of 2 bad answers then eliminated them all.

You wrote:

"At least some spring clean up participants are not active in the town's artistic circle.
(PTSCsome/TAC)"

See there was a subtle switch here.
You represent NOT active in towns artist circle as
TAC (aka are active, we cannot do that, they mean opposite things). When it should be
-TAC or ~TAC.

This is why the answer choice B is wrong.

When you look at my initial map of course I see there is an overlap between not active in the art circle, spring cleanup and certificate. Any of these three could be combined to make a some statement.

Spring Cleanup
|-----------------|---------------|
Certificate
<------------------------------->

Not Active in the art circle (some but some can mean all as well)
<------------>


When I finished this question, I predicted the answer would be some who got certificates are NOT active in the town's artistic circles. That would be a perfect inference

But look at the answer choice B

"Not all of those who receive community recognition certificates are active in the town's artistic circles. Not all implies what? Some"

I agree not all =some in lsat language.

So some who get a certificate are active in the town's circle is not a MBT. You'd have to assume to know something about a group you know NOTHING about. People who are ACTIVE in the town art circles.

The closest we get to being active in the towns art circle is being told about the downtown fair. Which is implied to mutually exclusive with the cleanup (and therefore we cannot infer anything about it) ie

Spring Cleanup
|----------|---------|
Certificate
<------------------>

Not Active in the art circle (some but some can mean all as well)
<--->

Downtown fair (assumed to be in active art circle)
|--------------------->

So some who got a certificate are NOT active in the town's artistic circles. The answer choice either has a typo or is a could be true. It could be true that you went to the downtown fair and are active in art circle and got a certificate (if you assume the fair and cleanup are not exclusive). But the inference is fair and cleanup were exclusive. It also could be true you got the certificate went to the cleanup and then went to the fair and are thus active in the art circle. That would make B the guaranteed answer. The problem is D COULD be true too. If you got the certificate you COULD have gone to the cleanup. So you have 2 could be true answers to a must question.


answer choice B is wrong because it says this MUST be true


Spring Cleanup
|----------|---------|
Certificate
<------------------>

Not Active in the art circle (some but some can mean all as well)
<--->

Downtown fair (assumed to be in active art circle)
|--------------------->

B says some who got a certificate MUST have been active in the art circles (presumably attended the fair). I agree it could be true. But it is not a must be true. The mutually exclusive way above is actually implied because the question suggest the fair and then cleanup were not plausible to be attended at the same time.

ENTJ

No. I represented "not active town's artistic circle" as "/TAC".

/TAC means Not TAC.

Luluc1234

OP review the Valid Argument Form 4 in the "Some and Most Relationships." The inference (B) in this Q is very clear. (D) is reversal of the first sentence.

c.janson35

I think the issue here is with your interpretation of the phrase "not all". Not all translates into "some...not" rather than just "some."

In regards to this question:

B states: "Not all who receive certificates are active in circles" which is the same as "some of those who receive certif are not active in circles," which is the inference you get by putting together /A some P and P-->RC.

c.janson35

Also, as @Luluc1234 points out about answer choice it is the reversal of the first sentence, and incorrect reversals can never be the correct answer because it is a logical flaw to change A-->B into B-->A, so keep an eye out for these kind of choices.

jmac800

@ entj,

"What does answer choice B say? Not all of those who receive community recognition certificates are active in the town's artistic circles. Not all implies what? Some.

RCRCsome/TAC. "

I understand that some who get a certificate MUST overlap with some who are not active in the artistic circles. That certainly is clear. But that is not what answer choice B says. It says not all (some) who got a certificate are active in the towns circle. See you even repeated the language shift error above. The right must be true inference would be some who got a certificate are NOT active in the town's circle. You even wrote this as RCRCsome/TAC, so I know conceptually you agree with me. My issue isn't with the concept, it is with the wording of the answer. The problem is the answer choice B doesn't say that. It says the opposite. It says Not all (Some) who receive the certificate are active in the town's artistic circles. Answer choice B says RCRCsomeTAC. It isn't saying /TAC. And we know nothing about people in the artistic circles.

@c. janson 35. If not all = some...not then yes B certainly is the correct answer. My question would then be how do you know not all =some...not. Is there a particular lesson I missed that it was in?

Also could you explain your abbrevations below, I am somewhat confused as which means which. ie which is /a and some p, and rc? thanks.

"which is the inference you get by putting together /A some P and P-->RC."

ENTJ

@jmac800 I see your confusion. If you read what I wrote before carefully, you'll see that I mentioned that a some statement is reversible. What does this mean? The "/TAC" and "RCRC" variable stays the same. The only change is they switch positions in a some statement.

It doesn't matter if it's :/TACsomeRCRC OR RCRCsome/TAC. They logically mean the same thing because some statements DO NOT have contrapositives.

All statements such as D are not reversible and can't be confused for the rules permitted with some statements.

AsomeB is the same as BsomeA.
Asome/B is the same as /BsomeA
/AsomeB is the same as Bsome/A
/Asome/B is the same as /Bsome/A

Check out this lesson: http://7sage.com/lesson/some-statements-translation/

c.janson35

@jmac800:

"Not all cats are dogs"

This doesn't mean some cats are dogs, because some could logically equal 100% which would not be "not all". Not all cats are dogs means that there are some cats who are not dogs. Put another way: all cats are dogs would mean that 100% of cats are dogs. But not all cats are dogs means that some percentage less than 100 of cats are dogs, because not all means less than 100. But this percentage could be 0% in which case saying "some cats are dogs" would be invalid. By saying some cats are not dogs then you account for the possibilities from 1% to 100% of cats who are not dogs, which gets us back to the original not all phrasing.

What's important is that you can't just ignore the negative in the sentence. "Not all X are Y" does not mean that some Xs are in fact Ys. If you were to draw a Venn diagram you could draw two completely separate circles for X and Y and it would be true that not all X's are Y's without being true that some X's are Y's.

Hope this helps!

jmac800

Thank you C janson, The some...not version is actually very clear, and your example of cats and dogs was useful. It allowed me to solve the question conceptually as well.

@eEntj. I agree the right inference is /TACsomeRCRC OR RCRCsome/TAC. Either way makes no difference. I just don't agree with you that, this is what B is saying. B doesn't say anything about not active people. It tells you about active people. I think you are actually misreading the answer choice if you think it does.

The reason this is a difficult question is because the writer of this question attacked it from the other side that we are use to with inference questions. I took me two hours thinking about it and reading what C janson wrote but there are several to go about solving this, and I am posting them just for any future test taker.

Spring Cleanup
|------------------------------|-------------------------|
Certificate
<------------------------------------------->

Not Active in the art circle (some but some can mean all as well)
<----------------->

B says nothing about people who are Not Active in the art circle. What B IS saying is that Not ALL the people who got a certificate ARE active in the art circle. What this really means is that EVERYONE who got a certificate CANNOT be in the art circle. Why? Because if this were true, then the Not Active in the art circle line would be pushed out from getting certificates and cleanup. Because all certificate people active in the art circle

Spring Cleanup
|------------------------------|-------------------------|
Certificate
<-----------------------------|-------------->

Active in art circle
<------------------------------------------------>


Not Active in the art circle (some but some can mean all as well)
<----------------->

This would tell us that those not active in the art circle cannot have a certificate. And that simply cannot be true based on the information from the passage. Therefore since it cannot be true, we know there must be at least 1 guy who has a certificate and is not active in the art circle. Then all of them can not be active in the art circle. Which is why NOT ALL those with certificate must be in the art circle. If that were the case it just makes the Not active and certificate holding possible.

Although for this question, I prefer C. Janson way of solving it, because it is conceptually difficult to grasp in the minute you have on the LSAT question to figure this out. So it is far easier to just recognize, not all = some...not and solve it.