PT21.S2.Q03 - a new medication for migraine

zkchrumz

I find abstract FL AC's to be quite a hassle on the LSAT. Usually I POE it down to one answer, which feels right, but I don't work through the FL if I feel it'd be a super time sink. So I BR and work it out then (now). I'm talking about AC B here, "No migraine sufferers with heart disease will take the new medication except under careful medical supervision." The no makes it a not both relationship: IF MIG sufferer w/ HD -> NOT take medication. The "except" gets translated to an IF NOT, which now becomes a joint sufficient condition: IF NOT under supervision.
SO, in total:
IF MIG sufferer w/ HD
+ -> NOT take medication
IF NOT under supervision

How is my methodology?
https://7sage.com/lsat_explanations/lsat-21-section-2-question-03/

inactive

Bumping so more people can see this. (Also edited your title to better fit our rules)

jknauf

Hey @zkchrumz

I'm hesitant to answer because I'm not entirely sure, but I don't think we need to make this into a not both relationship.

So for the stimulus we have: If patients with heart disease take medication under supervision --> No side effects

Conclusion: Concerns about side effects are unfounded

The assumption here is that our conditional relationship is true, so we are assuming if they are taking the meds they are taking it under supervision.

(It seems like you easily understood this and are just asking about your methods, but just bare with me for the sake of thoroughness!)

B: No (negate following conditional) migraine sufferers with heart disease will take the new medication EXCEPT (I just translate this to unless in my head but, either way, this is negate sufficient, so we get rid of our already negated statement, two negations = a positive) ---> under careful medical supervision.


So our confusion here is separating the sufficient into two different groups. Our group is Migraine sufferers with disease who take meds. B is stating if they are part of this group (Migraine sufferers with disease who are taking meds) If they are part of this group ----> they are under supervision.


Lets talk through this as it doesn't appear we are going to get much help =]

zkchrumz

@"Dillon A. Wright"
Thank you for the assistance. I'll try to remember the format.

@jknauf
For the not both, I'm referring to what JY calls the group 4 logical translation (not both rule). He uses it here https://7sage.com/lsat_explanations/lsat-6-section-4-game-4/ on question 24, which I just watched coincidentally. If we say "no cat is a dog", what we're really saying is that there is no thing that is both a can AND a dog. If it's a cat, then it cant be a dog, cause no cat is a dog. If it's a dog, then it can't be a cat, contrapositive, no dog is a cat.

Also, I think that the error in the problem is that the author is assuming that the following situation is impossible, "People with heart disease take the medication but are not under medical supervision." I find his formal logic to be fine, no flaw there. Just making sure that the logic is actually engaged is the problem. Which is what B does, albeit a bit convolutedly.

@jknauf said:
B: No (negate following conditional) migraine sufferers with heart disease will take the new medication EXCEPT (I just translate this to unless in my head but, either way, this is negate sufficient, so we get rid of our already negated statement, two negations = a positive) ---> under careful medical supervision.

I could be wrong, but I don't think that the except can directly negate the necessary here, because there is already a sufficient attached to it. We agree up to "If migraine sufferer with heart disease -> will NOT take the new medication." The except (i just read as unless/if-not) negates the condition immediately following it and makes it the sufficient, because the necessary is already set up as "will NOT take the new medication". If we use the "unless equation" as you say (which I am not sure is allowable), then we end up with "If migraine sufferer with heart disease + If they are under medical supervision-> will NOT take the new medication." Which, as you say, reinforces the FL in the problem, but as I said above, I don't find the FL in need of help, it's making sure that the FL always triggers. So, in summation, I can understand where the interpretation comes from, and it's purely coincidence (maybe? tricky LSAC) that it reads that way when we do some fancy (fallacious?) negations.

As an aside, I love it when the autocorrect tries to tell me "contrapositive" should be "contraceptive" or "contravention", but completely leaves my apostrophe-less conjunctions alone! Oops... Also, convolutedly is definitely a word, though more of a British variant apparently.

dcdcdcdcdc

"No migraine sufferers with heart disease will take the new medication except under careful medical supervision"

I read this as a group 4 (negate necessary) indicator followed by a group 3 negate sufficient indicator. I did not break "will" out as a necessary condition indicator but instead contained it within the subject.

As a result, as written, (B) diagrams as follows:
migraine sufferer with heart disease taking the medication --> medical supervision

I believe this relationship is pretty clear from a reading of (B) as written. We can grasp that the statement is saying that if one is taking the medication and is a migraine sufferer with heart disease, then one does so with medical supervision; i.e., there does not exist a person who is a migraine suffered with heart disease taking the medication yet is not supervised.

Since (B) translates nicely to an if A, then B statement (basically all A are , we can easily apply the negation of this statement, as follows:

Some migraine sufferers with heart disease taking the new medication do so without medical supervision.

Check the conclusion of the stimulus: We should not be concerned about these issues (and the stimulus provides support that medical supervision contains the issue).

Ok, so if (B) is not the case (we apply the negation test) then we have some people who are NOT receiving the medication under medical supervision. I think in this case we should definitely be concerned about the serious effects and, thus, the conclusion in the stimulus does not follow from the premises. The argument relies on the assumption given in (B).

zkchrumz

@dcdcdcdcdc
I think our approaches are fundamentally the same, the only difference being that I keep the sufficients separate, whereas you combine them. In retrospect, I like the idea of combining them like you did, it certainly makes taking the contrapositive simpler. However, I find that my mind generally doesn't tend to combine multiple sufficients into one; I think maybe it conflicts with my internal logicometer on the LSAT, which usually says that if you simplify something you tend to lose some degree of precision. That having been said, I don't think that is the case here. Thanks for your take.

dcdcdcdcdc

@zkchrumz

I'm with you on combining things. Never would have been comfortable doing this before seeing a bunch of LR questions where I was over complicating things by separating out the items into embedded conditionals. In this case, as you mentioned, simplifying gets the job done.