Anyone who fails to answer a patient’s questions cannot be a competent

Classic “If/Then” type of formal logic that shows up on many LSAT questions

Not as important when it comes to GMAT questions.

However, the question is a good exercise for the brain

Posted from my mobile device

I always falter in these If/then questions.
The question mentions that there is flawed reasoning which we must identify in the choices, the one that parallels that reasoning is our choice.

However, what is the flaw in the original argument.

I explained this in a post earlier in this thread. This question tests one of the most common logic errors people make in day-to-day life, an error I think. you could be almost certain to see on any LSAT test. The error isn't tested nearly so often on the GMAT, and when it is, it's usually well disguised, so this question is one of those obviously-LSAT questions that won't be similar to any GMAT question you're likely to encounter.

The error is this: when a sentence that reads "If X is true, then Y is true" is logically correct, often people with think the logical "converse" is correct too: "If X is not true, then Y is not true". But the converse is not generally correct; it might be, or it might not be. So this sentence is presumably true:

If I go swimming, I get wet.

But if you take the converse, you no longer get something that is true:

If I don't go swimming, I don't get wet.

because people get wet when it rains or in the shower, say. What you can correctly infer, from a true sentence that says "If X is true, then Y is true", is something called the logical "contrapositive", which is a lot like the converse, but you need to flip the 'X' and the 'Y' -- the contrapositive here is "If Y is not true, then X is not true". Applying that to the first sentence above, you'd get this:

If I'm not getting wet, I'm not swimming.

which must be true if the original sentence is true. This question makes the same error: "If a doctor does not answer questions, the doctor is not competent" becomes, in the conclusion of the argument, its (logically incorrect) converse "My doctor answers questions, so my doctor is competent". That may or may not be true. What must be true is the contrapositive, but this isn't what the argument concludes with: "If a doctor is competent, that doctor answers questions." A doctor might need a whole lot of other skills and qualities, besides answering questions, to be competent though.

Hey Ian,
Thanks for taking time to answer my query.
I read your earlier post and like it but could not understand the flaw in the argument.

"Anyone who fails to answer a patient’s questions cannot be a competent physician. That is why I feel confident about my physician’s competence: she carefully answers every one of my questions, no matter how trivial."

In the passage i took the matter as fact and didn't question it, and i think thats the reason i didn't notice the flaw. However, i am averse to this kind of question which is also the reason for my faltering. The moment i read something like "draws similar line of reasoning or parallells", i get jitters and most likely make a mistake.

Once again thanks for rephrasing the crux of the argument. I feel so dumb now as the reasoning looks so obvious.

The good news is, if you're taking the GMAT, it's very rare to see questions that are like this at all. I've maybe run into one or two official questions, out of thousands, that I'd say are similar to these LSAT parallel reasoning problems. So it's nothing to be concerned about. If, however, you're preparing for the LSAT, then you'd want to get comfortable with this type of question.

This question tests identifying which answer choice confuses a "necessary" condition with a "sufficient" one.

The correct answer essentially says, "having, at most, one job is necessary to find balance; Jane has one job, therefore, she definitely has balance."

There are potentially a million OTHER factors which dictate whether Jane will have balance.

The logic is parallel to saying, "having a good education is necessary to become a self-made millionaire; John has a good education therefore he WILL become a self-made millionaire."

KarishmaB Ma'am,

In option B,
Anyone who is not in favor of the proposal is ill informed.
Necessary condition is taken to be sufficient. A person is not in favor, hence he is ill-informed.
Jeanne opposes the proposal, hence she is ill-informed.

In this scenario too, we are taking a necessary condition to be sufficient.

Please evaluate my reasoning.

Thanks

KarishmaB Ma'am,

In option B,
Anyone who is not in favor of the proposal is ill informed.
Necessary condition is taken to be sufficient. A person is not in favor, hence he is ill-informed.
Jeanne opposes the proposal, hence she is ill-informed.

In this scenario too, we are taking a necessary condition to be sufficient.

Please evaluate my reasoning.

Thanks

If someone is not in favour, he is ill informed

Not in favour leads to being ill informed. So this is a sufficient condition.
If A is not in favour, we can correctly say that A is ill informed.
There is no flaw in this logic.

Note the wording of the original argument: If A (fails to answer), then cannot be B (competent).
So answering is necessary for being competent. It doesn't say that 'fails to answer' implies 'incompetent'. It just says that 'fails to answer' implies that one cannot be competent. So answering is necessary for competency.

Note the wording of option (B): If A (not in favour), then B (ill informed)
Being 'not in favour' leads to being ill informed (is sufficient to be ill informed)