Critical Reasoning

I meet this thread regarding sufficient assumption.

testluv, friends. we do not need to study sufficient assumption for gmat. Is that right?





heshamelaziry wrote:
THanks. Is there a way to differentiate between necessary assumption and sufficient assumption ?
Hi Hesham,

Of course. It would be unfair of the test-maker to leave it open to interpretation whether the question was asking for a necessary or sufficient assumption.

A question that asks you for an assumption that the argument DEPENDS on, RELIES on or is REQUIRED is a necessary assumption question. We can call these "necessary" words.

Sufficient assumption questions are usually phrased like this: "which of the following, if assumed, would enable/allow the conclusion to follow".

A necessary assumption is something that without it--if you did not have it--the argument would no longer hold (would fall apart). (That's why we can use denial test in necessary assumption).

A sufficient assumption is something that with it--if you had it--it would guarantee that the argument would hold. (That's why denial test isn't very helpful in sufficient assumption.)

And, because necessary assumption questions are so much more common, if you are not sure, then it is probably a necessary assumption question.

Let's consider an example. Here is a sample argument:

"The average 40 year-old North American male will have watched one million TV commercials in his or her lifetime. We may safely conclude, therefore, that the TV commercial has influenced North American habits of thought."

Now, here are two statements:

I Anything people are exposed to ingreat quantity will influence habits of thought.

II Certain forms of communication to which certain people are subjected will affect their habits of thought.

The first statement is a sufficient assumption. If it were true that ANYTHING in great quantity will influence thought, then since the TV commercial counts as "anything," if we plugged this into the argument, then the conclusion certainly follows. But it is not necessary--the argument does not necessarily fall apart without this statement. His argument does not NEED the assumption that ANYTHING in great quantity will influence habits of thought. (This is why extreme is usually wrong in necessary assumption but not in sufficient assumption questions.)

The second statement is a necessary assumption. He HAS to assume that certain (ie, some = at least one) forms of communication (TV commercials among them) has the ability to influence habits of thought. If he did not assume this--if we to were to take it away (ie, deny it)--then the argument falls apart! But it is not sufficient. If we plugged it in, the conclusion does not for sure follow because we don't know if TV commercials count as "certain forms".
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Kaplan Teacher in Toronto

testluv, friends. we do not need to study sufficient assumption for gmat. Is that right?

Question 58 on page 502 of OG 12 is an example of a sufficient assumption question.

As I believe I said in my post above, sufficient assumption questions are a lot less common than necessary assumption questions. But they still are a GMAT question type in CR.

testluv, if that is a Sufficient Aassumption, then why does the correct answer choice on negation make the argument weak.
Also, is there any strategy to solve an Assumption Question of Sufficient when the answer choices contain both necessary and sufficient answer choices??

Thanks