LSAT Blog wrote:These are one of the few question-types I often diagram.
What you're describing is the most common format for these types of questions, but not the only format. The correct answer to a Sufficient Assumption (Justify) question is often simply a restatement or the contrapositive.
I'm going over the most common format with formal logic, then with a few examples from real PT questions:
Evidence: A ---> B
Conclusion: C ---> B
Sufficient Assumption #1: C ---> A
Sufficient Assumption #2: NOT A ---> NOT C
Contrapositively...
Evidence: D ---> E
Conclusion: D ---> F
Sufficient Assumption #1: E ---> F
Sufficient Assumption #2: NOT F ---> NOT E
Thanks to Steve's JTC example from another thread, I was able to solve S1, Q25. It seemed really complex to get through, and I'm not sure if I would be able to do this under timed conditions, so if someone has an easier method than the one I outline below, please share!
PT 58, S1, Q25
If a wig has any handmade components, it is more expensive than one with none. Similarly, a made-to-measure wig ranges from medium-priced to expensive. Handmade foundations are never found on wigs that do not use human hair. Furthermore, any wig that contains human hair should be dry-cleaned. So all made-to-measure wigs should be dry-cleaned.
P1: Wigs with handmade components --> More expensive than non-handmade
P2: Made-to-measure wigs --> Medium-priced to expensive.
P3: Handmade components --> Wigs with human hair.
P4: Wigs with human hair --> Dry-cleaned
Conclusion: Made-to-measure wigs --> Dry-cleaned
Sufficient Assumption: Made-to-measure wigs --> Wigs with human hair
Correct Answer Choice (A): Any wig whose price falls in the medium-priced to expensive range has a handmade foundation. (Medium-priced to expensive --> Handmade components, which is the SAME as Made-to-measure wigs --> Wigs with human hair)
Answer choice (B): If a wig's foundation is handmade, then it is more expensive than one whose foundation is not handmade. (This is a restatement of P1, so it's wrong.)
Answer choice (C): A wig that has any handmade components should be dry-cleaned. (This is a combination of P3 and P4 and includes a common element from the conclusion, so it's wrong.)
Answer choice (D): If a wig's foundation is handmade, then its price is at least in the medium range. (Wrong. Made-to-measure wigs are in medium to expensive range.)
Answer choice (E): Any wig that should be dry-cleaned has a foundation that is handmade. (Wrong because it's a Mistaken Reversal of P3 and P4.)