Q5 - Sickles and Harvesting

[nandy_millette]

Got this one correct so decided to help future test takers:

Context: Sites 1 has sickles with scratches, Sites 2 did not
Premise: Sickles with scratches means Sickles used for harvesting because harvesting cause scratches
Conclusion: At Site 1 Sickles used for harvesting but not at Sites 2

This entire argument is based on the Premise so to weaken the Argument you have to weaken the premise/evidence and show that in some cases you can have Sickles with Scratches but not caused by harvesting or Sickles used for harvesting but no Scratches

A-Sickles at site 1 which have not been found but do not have sickles- who cares? Lets just focus on the ones that we know about, which in this case have scratches

B- The scratches on the Sickles at Site 1 were not caused by harvesting--- so your telling me that we can have Sickles with scratches but not caused by Harvesting, so then we cannot conclude Scratches therefore Harvesting BINGO correct answer

C-Regardless of harvesting use, the sickles at both sites were used for rituals-- Oh this sounds goods so maybe the rituals caused the scratches..hmm well then there should be scratches on the sickles at Site 2 but there aren't so this is a wrong answer

D-At the second site other tools were used for harvesting..okay cool but still does not weaken the evidence

E-Who cares about the manufacturer of the sickles--wrong!

[maryadkins]

Thanks for this explanation. It's great. I just want to clarify one thing about what you said here:

This entire argument is based on the Premise so to weaken the Argument you have to weaken the premise/evidence and show that in some cases you can have Sickles with Scratches but not caused by harvesting or Sickles used for harvesting but no Scratches

We actually don't have the option of choosing an answer choice that tells us sometimes there is harvesting but no scratches. Why? Because the stimulus tells us that "whenever they are used to harvest grain" they become scratched. In other words, we can diagram this conditionally as:

Harvest --> Scratched

The mistake this argument makes is reversing that logic:

Scratched --> Harvest

That's not valid. (B) captures this flaw.

[Bluegrace17]

That is not the correct answer. For answer choice "C" we can eliminate it because ritual uses is not relevant to our argument. The correct answer is "B". They simply confuse the sufficient and necessary condition which I agree it. Let me explain how: The first line gives us a premise distinguishing two sites.
One with S and one with not S.
They then give us a conditional whenever HG then S
Before we look at the next line we can already assume this is about to be a flawed argument. Why?
Well the first site we are given a sufficent condition but the conditional is about a necessary condition. We cannot properly infer because basically there are many other ways to scratch a sickle blade besides harvest grain on it. However the second argument actually works. If we don't have S the necessary condition then we can 100% fail the sufficient condition. So site 2 makes sense. We would attack site 1 because it is flawed.

[maryadkins]

I mistyped! Sorry about that. The correct answer is (B). I just fixed the post above to indicate that the answer is (B).