Last year, a software company held a contest to generate ideas for the

Question

Last year, a software company held a contest to generate ideas for their new logo. According to the rules, everyone who entered the contest would receive several prizes, including a T-shirt with the company’s new logo. Juan has a Tshirt with the company’s new logo, so he must have entered the contest.

The reasoning in the argument is flawed in that the argument

(A) infers a causal relationship when the evidence only supports a correlation

(B) takes a condition that is sufficient for a particular outcome as one that is necessary for that outcome

(C) infers that every member of a group has a feature in common on the grounds that the group as a whole has that feature

(D) has a premise that presupposes the truth of the conclusion

(E) constructs a generalization on the basis of a single instance

ankushsambare · Answer

The question is asking what the flaw is.
Key point: The rule says "if you entered, you got a T-shirt," but the argument assumes "if you have a T-shirt, you must have entered." That is confusing sufficient with necessary.

(A) About causation vs correlation – not relevant.
(C) About group-to-individual – not applicable.
(D) Circular reasoning – not the case here.
(E) Single instance generalization – not happening.

Answer: (B)

Deep1208 · Answer

I did answer the question,but I would like to get a detail explanation of the same.
Thank you in advance!

egmat · Answer

Deep1208  Here's how I'd break this down:

The Argument's Structure:

The argument follows this logical pattern:
 
  Premise:  If you entered the contest → you receive a T-shirt (along with other prizes) 
  Observation:  Juan has a T-shirt 
  Conclusion:  Therefore, Juan must have entered the contest

The Flaw - Sufficient vs. Necessary Conditions:

This is a classic case of confusing  sufficient  and  necessary  conditions:

Sufficient condition:  Entering the contest is  sufficient  to guarantee getting a T-shirt (if you enter, you  will  get one) 
  Necessary condition:  The argument incorrectly treats entering the contest as  necessary  to have a T-shirt (if you have a T-shirt, you  must have  entered)

Why this is wrong:  Just because entering guarantees a T-shirt doesn't mean it's the  only  way to get one. Juan could have:
 
 Received it as a gift 
 Bought it from someone 
 Been given one as an employee 
 Found it, etc.

The Answer: (B)

Choice (B) perfectly describes this flaw: " takes a condition that is sufficient for a particular outcome as one that is necessary for that outcome "

The argument takes entering the contest (sufficient for getting a T-shirt) and incorrectly treats it as necessary (the only way to have a T-shirt).

How to Spot This Flaw Pattern:

Watch for arguments that follow this structure:
 
 If  A , then  B  (given) 
  B  is true (observation) 
 Therefore,  A  must be true (conclusion)

Recognition trigger:  When the conclusion uses words like "must have," "definitely," or "certainly" to move backward from an outcome to a cause, ask yourself: "Is this the  only  way this outcome could occur?"

If other explanations exist, the argument is likely confusing sufficient with the necessary conditions. I hope this helps!

Last year, a software company held a contest to generate ideas for the

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