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Okay, so I can pretty much get 83% of assumption questions right at this point, but I'm at 40% with Justify the Conclusion. I have a hard time diagramming these questions, and I re-read the LSAT Logical Reasoning Bible over twice and I just don't get these type of questions.

I understand that we're linking two parts of the stimulus, the new information in the conclusion with the information in the premises. I just can't seem to do this quickly enough and sometimes I have a real hard time diagramming these out.

Any thoughts? I've read some of the tips on this question type on the forum and it didn't seem that helpful.

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



Examples:
PrepTest 31 (June 2000), Section 2, Question 10, p91 in Next 10

Evidence: JR ---> NOT D
Conclusion: FP ---> NOT D

Sufficient Assumption: FP ---> JR


PrepTest 35 (October 2001), Section 1, Question 22, p226 in Next 10

Evidence: P -> T -> NOT C OR C -> NOT T -> NOT P
Conclusion: P ---> NOT H OR H ---> C

Sufficient Assumption: NOT C ---> NOT H
Sufficient Assumption: H ---> C



In a more general sense, the most common formats for Justify the Conclusion (aka Sufficient Assumption) questions, are (in order of complexity):

1. restatement of conclusion / arg
2. contrapositive of conclusion / arg
3. the format in the post I linked above

I've found the 3rd format to be the most common.


I think of Sufficient Assumption Qs as providing information that, if true, would be Sufficient to support the conclusion 100%.

In other words, this information, if true, will guarantee the conclusion's validity.



HTH

-Steve

Does anyone have a mental frame-work of how to approach these questions?

For example, with assumption questions, I think about it as a foundation for the argument being built. I am looking for an answer that must be true for the argument to work, and without it the argument falls down.

What is the mental framework for Justify the Conclusion questions?