5th edition question

[DavidH327]

Hello,
On the page 81 Q3 last answer choice which said Sufficient Assumption, why can't it be a necessary assumption?
By doing a negation, wouldnt argument fall apart?

Also, does negation only used to test necessary assumption not sufficient?

Thank you.

[ohthatpatrick]

The negation test is only for Necessary Assumption. You could really re-brand it "the Necessity test", since you test necessity by taking something away and judging whether it was really needed in the first place.

The problem with the last answer on Q3 is that it's way too broad/extreme to be a Necessary Assumption.

The author is only talking about the last couple months and about Chad's. He doesn't have to assume that for ALL restaurants, for EVERY SINGLE difference in revenue ever, you can explain it by number of burgers. (After all, think of all the restaurants that don't even sell burgers!)

Negating that answer says, "At least one time in history, a difference in monthly revenue was not explainable by number of burgers". Would that badly weaken his argument about Chad's Burger Shack?