Suffecient Vs Necessary

[heshamelaziry]

By reading the question stem, how do we know if the question is asking for sufficient or necessary assumption ?

Thanks to all.

[shadowsjc]

you shouldn't think of questions in term of sufficient or necessary. the best tip for CR questions is to identify which of the main question types (must be true? cannot be true? weaken, strengthen, etc. ) it's asking. it would be too long to post tips for all of them here, but the Powerscore Critical reasoning bible was very helpful in this regard and i'd recommend you read through it for this section.

knowing the difference between sufficient and necessary is a useful tool to know when eliminating answers, but i don't think it's all that helpful in reading the question stem.

[heshamelaziry]

you shouldn't think of questions in term of sufficient or necessary. the best tip for CR questions is to identify which of the main question types (must be true? cannot be true? weaken, strengthen, etc. ) it's asking. it would be too long to post tips for all of them here, but the Powerscore Critical reasoning bible was very helpful in this regard and i'd recommend you read through it for this section.

knowing the difference between sufficient and necessary is a useful tool to know when eliminating answers, but i don't think it's all that helpful in reading the question stem.

Thanks.

I have the CR BIBLE, but i didn't see where in the assumption section it shows the difference between necessary and sufficient assumptions answer choices. Almost all assumption questions don't have the word "necessary" in the stem.
If you like you can tell me what pages, maybe i miss interpreted it to be something else or so.

Another issue I have with the CR Bible with regards to assumptions is that it says that almost always the assumption can be found by identifying the Cause and Effect in the conclusion. However, I found that many enough questions have the correct answer in the premises, where the assumption is deduced from them and consequently making the conclusion more sound.
My proof is the type of stem that asks the following: " the conclusion above can not be true unless which of the following is true ?"
What are your thoughts about this ?

[shadowsjc]

Hi,

I unfortunately sold my copy of the CR Bible already, so I can''t reference any specific pages. However, I think you're dwelling too much on the whole concept of Sufficient vs Necessary.

If A -> then B

A is sufficient, B is necessary.

On the GMAT, they won't ask you specific questions about which is which. It's useful to be able to differentiate which is which in some questions.

I don't remember ever encountering a question where the answer is just a restatement of one of the premises. Can you post a full question and answer choices of an example so I can see what you're talking about? Usually the questions that say "the conclusion can not be true unless which of the following is true" have answers that are not stated in the passage.

[heshamelaziry]

Hi,

I unfortunately sold my copy of the CR Bible already, so I can''t reference any specific pages. However, I think you're dwelling too much on the whole concept of Sufficient vs Necessary.

If A -> then B

A is sufficient, B is necessary.

On the GMAT, they won't ask you specific questions about which is which. It's useful to be able to differentiate which is which in some questions.

I don't remember ever encountering a question where the answer is just a restatement of one of the premises. Can you post a full question and answer choices of an example so I can see what you're talking about? Usually the questions that say "the conclusion can not be true unless which of the following is true" have answers that are not stated in the passage.

For Example:

The Highway Safety Institute reports that the PZ 1000 has the fewest injuries per accident of any car in its class. This shows that the PZ 1000 is one of the safest vars available today.

The stem asks which answer weakens the argument. My frist Cause and Effect notes were this: Cause: PZ 1000 has less injuries than cars in its class. Effect: PZ 1000 is one of the safest cars.

So using the CR BIBle techniques I tried to show that there is another reason the car is safe or that maybe the relationship is reversed or other cars(not in its class were safer). However, the answer compares the PZ 1000 to cars in its class, which is in the premise. This is the answer:

CArs in in the class to which the PZ 1000 belongs are more likely to be involved in accidents than are other types of cars.

Another example is question 22 in GMAT verbal.

Hope I make sense, or maybe I am digging too much. Thanks for your help and Congrats on your amazing GMAT score.