Critical Reasoning

In recent years, a village outside Osaka, Japan has taken to hosting a ninja festival, a celebration of Japan's heritage that reflects on its feudal past while exalting its pop culture driven present. But clearly only children take this festival seriously, for they are the only attendees who bother to dress up as ninjas.

Which of the following is an assumption on which the argument depends?

Any attendee who dresses up as a ninja takes the festival seriously.

No attendee who takes the festival seriously would fail to dress up as a ninja.

Anyone who is not dressed up as a ninja is not attending the festival

The festival organizers have instituted a ninja-themed dress code.

If an attendee is not dressed as a ninja, then that attendee will not be taken seriously by other attendees.


Please elaborate necessary condition here.

imskpwr wrote:In recent years, a village outside Osaka, Japan has taken to hosting a ninja festival, a celebration of Japan's heritage that reflects on its feudal past while exalting its pop culture driven present. But clearly only children take this festival seriously, for they are the only attendees who bother to dress up as ninjas.

Which of the following is an assumption on which the argument depends?

Any attendee who dresses up as a ninja takes the festival seriously.

No attendee who takes the festival seriously would fail to dress up as a ninja.

Anyone who is not dressed up as a ninja is not attending the festival

The festival organizers have instituted a ninja-themed dress code.

If an attendee is not dressed as a ninja, then that attendee will not be taken seriously by other attendees.


Please elaborate necessary condition here.

Premise: Only children dress up as ninjas.
Conclusion: Children are the only attendees who take the festival seriously.

Apply the NEGATION test.
When the correct answer choice is negated, the conclusion will be invalidated.
Answer choice B, negated:
Some attendees who takes the festival seriously fail to dress up as ninjas.
If the negation of B is true, then the argument cannot conclude that children dressed up as ninjas are the ONLY attendees who take the festival seriously.
Since the negation of B trashes the conclusion, B is the correct assumption: WHAT MUST BE TRUE for the conclusion to be valid.

The correct answer is B.

GMATGuruNY wrote: Premise: Only children dress up as ninjas.
Conclusion: Children are the only attendees who take the festival seriously.

Premise: Only children dress up as ninjas.
Conclusion: Children are the only attendees who take the festival seriously.

So, Premise-----> Conclusion
Since there is a clear cut SCOPE shift between Premise and Conclusion.

we an say, an assumption for the argument would be of this form:
"if ONE dresses up as ninjas, then ONE takes the festival seriously".

ie, "ONE dresses up as ninjas" is Sufficient condition for "ONE to take the festival seriously"

SO option A (Any attendee who dresses up as a ninja takes the festival seriously) will be correct.


On the contrary option B (contrapositive) is also correct as
"if ONE DOESNOT take the festival seriously , then ONE DOESNOT dress up as ninjas"...Contrapositive for the argument.

imskpwr wrote:

GMATGuruNY wrote: Premise: Only children dress up as ninjas.
Conclusion: Children are the only attendees who take the festival seriously.

Premise: Only children dress up as ninjas.
Conclusion: Children are the only attendees who take the festival seriously.

So, Premise-----> Conclusion
Since there is a clear cut SCOPE shift between Premise and Conclusion.

we an say, an assumption for the argument would be of this form:
"if ONE dresses up as ninjas, then ONE takes the festival seriously".

ie, "ONE dresses up as ninjas" is Sufficient condition for "ONE to take the festival seriously"

SO option A (Any attendee who dresses up as a ninja takes the festival seriously) will be correct.


On the contrary option B (contrapositive) is also correct as
"if ONE DOESNOT take the festival seriously , then ONE DOESNOT dress up as ninjas"...Contrapositive for the argument.

You have reversed the logic.

Premise: Only children dress up as ninjas.
Conclusion: Children are the only attendees who take the festival seriously.
Linking the premise to the conclusion, we get the following assumption:
Only attendees who dress as ninjas take the festival seriously.

Only B's are A's implies the following:
If A, then B.
Applying this reasoning to the assumption above, we get:
If an attendee takes the festival seriously, then he/she must be dressed as a ninja.

Answer choice A states the REVERSE of the assumption:
Any attendee who dresses up as a ninja takes the festival seriously.
Eliminate A.

I would discourage you from applying the rules of formal logic -- if-then statements, the contrapositive, etc. -- to GMAT CR's.
Such rules are far more relevant to the LSAT.

GMATGuruNY wrote:
You have reversed the logic.

Premise: Only children dress up as ninjas.
Conclusion: Children are the only attendees who take the festival seriously.
Linking the premise to the conclusion, we get the following assumption:
Only attendees who dress as ninjas take the festival seriously.

Only B's are A's implies the following:
If A, then B.
Applying this reasoning to the assumption above, we get:
If an attendee takes the festival seriously, then he/she must be dressed as a ninja.

Answer choice A states the REVERSE of the assumption:
Any attendee who dresses up as a ninja takes the festival seriously.
Eliminate A.

But, what about B in that case B is INcorrect.
B = If an attendee NOT takes the festival seriously, then he/she must NOT be dressed as a ninja

Correct contrapositive would be,
If an attendee NOT dressed as a ninja , then he/she does NOT takes the festival seriously.
ie NO attendee dressed as ninja would fail to take the festival seriously.

imskpwr wrote:

GMATGuruNY wrote:
You have reversed the logic.

Premise: Only children dress up as ninjas.
Conclusion: Children are the only attendees who take the festival seriously.
Linking the premise to the conclusion, we get the following assumption:
Only attendees who dress as ninjas take the festival seriously.

Only B's are A's implies the following:
If A, then B.
Applying this reasoning to the assumption above, we get:
If an attendee takes the festival seriously, then he/she must be dressed as a ninja.

Answer choice A states the REVERSE of the assumption:
Any attendee who dresses up as a ninja takes the festival seriously.
Eliminate A.

But, what about B in that case B is INcorrect.
B = If an attendee NOT takes the festival seriously, then he/she must NOT be dressed as a ninja

Correct contrapositive would be,
If an attendee NOT dressed as a ninja , then he/she does NOT takes the festival seriously.
ie NO attendee dressed as ninja would fail to take the festival seriously.

Answer choice B: No attendee who takes the festival seriously would fail to dress up as a ninja.
NO ATTENDEE WOULD FAIL TO DRESS UP means EVERY ATTENDEE WOULD BE CERTAIN TO DRESS UP.
Thus, B states the following:
Every attendee who takes the festival seriously would be certain to dress up as a ninja.
In other words:
If any attendee takes the festival seriously, then he/she must be dressed up as a ninja.
This is a perfect match for the assumption in the passage (highlighted in red above).

GMATGuruNY wrote: I would discourage you from applying the rules of formal logic -- if-then statements, the contrapositive, etc. -- to GMAT CR's.
Such rules are far more relevant to the LSAT.

Thanks a lot for the wonderful explanation.

But, I feel all of the CR question can be correctly answered if formal logics are known to one.
Still, I want to know why you are so apprehensive about formal logic.

There are 3 things to be considered while evaluating a formal logic.

Eg,If X happens,y will happen.
Negation:If X does not happen,Y will not happen.
Converse:If Y happens,X will happen.
Contraceptive: Y does not happen,X will not happen.

On GMAT,only CONTRAPOSITIVE is true.

[email protected] wrote:Hi imskpwr,

Formal Logic is a common "construct" on the LSAT, but is far rarer on the GMAT (chances are pretty good that you won't see Formal Logic at all on Test Day).

The GMAT does use a certain amount of "causality" in its CR prompts (causality is the idea that one thing will cause another thing to happen), but as noted, contra-positives and formal logic are not common. Emphasizing these subjects during your studies is not a good use of your time.

GMAT assassins aren't born, they're made,
Rich

I have seen some GMAT retired qs where FORMAL LOGIC is used.