StrengthenX vs. Cannot Be True

[rbolin]

I am having trouble being able to see the difference between StrengthenX and Cannot Be True. Can someone explain the difference?

[moshei24]

StrengthenX is basically "all of these CAN strengthen the argument except." So you're looking for four choices that make the stimulus stronger, and one that doesn't make it stronger. The one that doesn't make it stronger doesn't have to weaken it; it just can't strengthen it.

CANNOT Be True question, in my opinion, are a little trickier. You're not looking for four choices that could be true, and one that CANNOT be true. You need to find the choice that you could prove untrue based on the stimulus. So let's say the stimulus said that "you must be over 6 feet to play in the NBA." Which of following answer choices CANNOT be true?
(A) Bob can play in the NBA
(B) Jennifer can play in the NBA
(C) Don, who is 6'7 can play in the NBA
(D) Nick, who is 5'9 can play in the NBA
(E) Jasmine can play in the NBA

The correct answer is (D), because Nick is the only person we could prove from the stimulus CANNOT play in the NBA. He is not over 6 feet and therefore, we could prove that he can't play in the NBA. The rest could be true.

Does that help?

Please let me know.

[moshei24]

By the way, the way you would diagram the conditional statement I made in the sample stimulus would be like this:

Play in the NBA --> over 6 feet

and contrapositive:

over 6 feet --> play in the NBA

So anyone not over 6 feet CANNOT play in the NBA.

[Steve Stein]

I am having trouble being able to see the difference between StrengthenX and Cannot Be True. Can someone explain the difference?

Hi rbolin,

Thanks for your question. Those two question types come from two different families, which means that you should approach the two types very differently.

Strengthen X questions provide that all of the answer choices, if true, will strengthen the author's argument, except for one. The correct answer choice will be the only one that doesn't make the author's argument stronger.

So, in StrengthenX questions, you have to take each answer choice as true and assess each one's effect on the author's argument. Again, the one that doesn't strengthen will be the correct answer choice. In this sense, the one that doesn't add anything will be correct.

In Cannot Be True questions, on the other hand, the vital information resides in the stimulus. In response to these questions, the correct answer choice will be the only one that is inconsistent with the facts provided by the author. Thus, the correct answer will be one that directly contradicts information in the stimulus.

If you are thinking that the answer to a StrengthenX question must weaken the argument, that also isn't true (it can have no effect). But, for a moment, let's say that the answer does weaken the argument. Does that then make the two questions the same? No, but I can understand why they would feel that way. The difference is the matter of direction: a Weaken answer attacks the stimulus, whereas a Cannot answer is weakened by the stimulus.

I hope that's helpful! Let me know--thanks!

~Steve