Question Regarding Sufficient Assumption Drill #3 page 112

[Camiller]

Hi,

I have a question regarding one of the answer choices from #3 on pg. 112 of the 4th edition LR book (Chapter 3 Assumption Questions). Specifically, the solution states that the last answer choice is sufficient, and I wanted to verify that.

The answer choice states: "For any restaurant, any difference in revenue from month to month can be explained by a difference in the number of burgers sold."

The argument core:
The monthly revenue for Chad's Burger Shack was higher in July than April => Chad's Shack must have sold more burgers in July than April

Due to the difference in modality between the answer choice ("can be explained") and the conclusion ("must have sold"), I didn't think this answer choice was sufficient; just because a difference in revenue for a restaurant CAN BE explained by a difference in the number of burgers sold, does this necessarily entail that any difference in revenue MUST BE explained by a difference in the number of burgers sold?

Furthermore, the statement "any difference in revenue...can be explained by a difference in the number of burgers sold" does not necessarily entail that more revenue means that more burgers were sold, right? Per this language, the revenue for Chad's Burger Shack could have been higher in July than it was in April because it sold less burgers in July than it did in April, right?

So, is this really a sufficient assumption?

[ohthatpatrick]

Yeah, once again I agree with you.

I think the person writing the drill was trying to think of a way to be less direct and verbatim with regurgitating the wording from the argument, but I think both of your concerns are valid.

And Sufficient Assumption almost never takes chances with loose wording. I will forward this to the revision team as well.

[Camiller]

Phew. Thank you for your response. I thought I was losing my mind for a little.