Assumption Questions vs. Justify Questions

[abajaj]

I was going through the "Assumption Questions" practice questions in Lesson 5 and I noticed that a lot of the questions I got wrong were because I proved the answer to be 100% instead of between 0-99%, like you're supposed to do with assumption questions. I understand the theory behind it, but I seem to have a lot of trouble differentiating between what would be constituted as a "justify" answer and an "assumption" answer. Is there some way for me to know the difference?

[moshei24]

I'm going to take a stab at answering this question, because it's something that bothered me for awhile, and was something that for a long time I kept going over many times, so here I go.

Assumptions:

An assumption is something that has to be true if the conclusion is true. Like this:
ConclusionTrue --> AssumptionTrue

so in turn, you could use the negation method for an assumption question as follows:
If the assumption is no longer true, the conclusion would no longer be true. Like this:
AssumptionTrue --> ConclusionTrue

So when you look for the correct answer on an assumption question, you want to choose the answer that MUST be true given the conclusion of the stimulus. If the answer choice doesn't have to be true given the stimulus, it is the wrong answer.

For Justify questions, the argument is basically missing a piece in the argument and the answer choice fills it in.

Premises + Correct Answer Choice (Assumption) = Conclusion

When dealing with these questions, the mechanics are as follows:

AssumptionTrue --> ConclusionTrue

The assumption here is the correct answer choice. In my opinion, this is the easiest type of question to prephrase - you need to look for the missing piece in the argument, and that will be the answer.

Does that help?

FOR POWERSCORE INSTRUCTORS:
The one question that I would have about justify questions would be this: If the argument is missing a piece, why isn't that piece necessary for the conclusion to be true? Why is only sufficient?

[moshei24]

TYPO CORRECTION:

AssumptionTrue--> ConclusionTrue was a mistake.

For Justify questions it should really be:
AssumptionTrue--> ConclusionTrue

Sorry about that!

[Dave Killoran]

Think about Assumptions as minimalist answers. There can be nothing extraneous in a correct answer to an Assumption question—everything has to be something the author would rely upon in forming the argument. In this sense, the idea of must be true is correct, although it is something the author took as true while making the argument. If there are additional components, or statements that an author doesn't have to be committed to, then the answer will be incorrect.

When comparing that to Justify answers, the first point of confusion is that the two are often identical. That is, an answer could serve as an assumption or it could serve to justify the conclusion. But, while that is possible, it doesn't have to be that way, and Justify answers can contain additional, non-essential information. Let me use a rough example to explain this critical difference.

• Premise: I just bought two apples.
  Conclusion: Therefore, I own five apples.

An Assumption answer would be along the lines of:

• Answer: I already had three apples in my possession.

But, note that this answer would also serve as a correct answer in a Justify question. Thus, this is a good example of where they overlap.

Using the same argument as above, let's look at another answer:

• Answer: I already had three apples and two oranges in my possession.

This answer would be incorrect in an Assumption question, because the information about the two oranges is non-essential. But, in a Justify question, this would still be a correct answer because the information about the apples justifies the conclusion (and once that occurs, the information about the oranges is irrelevant).

Ultimately, this highlights the fact that assumptions are always about the minimalist answer where everything must be something the author fully believes in. Justify answers, on the other hand, can be like that, but they can also contain additional information--all that matters is that when added to the premises the answer produces the conclusion.

Please let me know if that helps. Thanks!

[moshei24]

Thanks, Dave! That answered my extra question, too!

[abajaj]

Thank you, Dave! That was very helpful.

So in summary - Assumption questions are the bare minimum (and really only the minimum) for what's required for the conclusion to be true. Justify questions have the extra push that completely prove for it to be true. Further assumptions are what happen while the author is forming the argument (so we really have to think about it from the author's perspective) and Justify questions really leave it up to us to figure out what the missing piece is.

[Dave Killoran]

I'd say that you more or less have it