Ann will either take a leave of absence from Technocomp and return in a year or else she will quit her job there; but...

Jborj653 on July 14, 2015

Diagram

Could you diagram this? Thanks

Naz on July 20, 2015

This is a strengthen with sufficient premise question. Remember that a sufficient premise is sufficient for a conclusion, if and only if the existence of the premise guarantees or brings about the existence of the conclusion. Therefore, we need to find the premise that 100% guarantees the conclusion. The way you want to attack these answer choices is two-pronged. Ask yourself, does it strengthen? If it doesn't, then cross it out and continue to the next answer choice. If it does strengthen, however, then ask yourself whether or not the premise guarantees the conclusion.

Let's diagram:

"Ann will wither take a leave of absence from Technocomp and return in a year or else she will quit her job there"

P1: not LA ==> QJ
not QJ ==> LA

"but she would not do either one unless she were offered a one year teaching fellowship at a prestigious university."

P2: TLA or QJ ==> 1YF
not 1YF ==> not TLA and not QJ

"Technocomp will allow her to take a leave of absence if it does not find out that she has been offered the fellowship."

P3: not FOF ==> ATLA
not ATLA ==> FOF

"but not otherwise,"

P4: FOF ==> not ATLA
ATLA ==> not FOF

"Therefore, Ann will quit her job at Technocomp only if Technocomp finds out she has been offered the fellowship."

C: QJ ==> FOF
not FOF ==> not QJ

Alright, so what's the issue here? Well, according to the conclusion, if she quits her job, then it must be true that Technocomp found out about her fellowship. However, from the info that we've been given, this doesn't necessarily need to be the case.

We know from P3 that if Technocomp doesn't find out about the fellowship, they will allow her to take a leave of absence. But, this doesn't necessarily mean that Ann will not still quit her job. We have no information telling us that is she is allowed to take the leave of absence, she will take the leave of absence, i.e. she will not quit.

This is exactly what answer choice (D) does for us.

(D): ATLA ==> TLA
not TLA ==> not ATLA

So, answer choice (D) strengthens the argument.

Now, does it guarantee the conclusion? Yes.

Remember, since we know that Ann will EITHER take a leave of absence OR she will quit her job, and since we know that in this context she cannot do both, Ann taking a leave of absence is the same as Ann not quitting her job. So, we can rewrite (D) to say: ATLA ==> not QJ, which allows us to connect P3 to (D) like so: not FOF ==> ATLA ==> not QJ in order to conclude: not FOF ==> not QJ, i.e. the contrapositive of the conclusion.