PT11.S4.Q13 - There are tests...

madman404

I'm not understanding why this question is A. I can tell in some capacity why it is correct, but it appears to simply restate information already present in the question (treating diseases is more expensive than preventing them).
On the other hand, B provides information that, if untrue, would fundamentally break down the structure of the argument (if it's more expensive to treat than to screen but screening does nothing, you have no choice but to treat anyway).

Why is B incorrect, and why is A correct if it doesn't provide any new information?

elevator_music

I would say this with regards to A and B:

A is the NA in this argument, and it's actually once that pops up pretty often on the LSAT, so once you get used to it, it becomes pretty obvious to note elsewhere. You say yourself that it is "restating" the information. That's good! It's a NA so sometimes it will feel like it's restating the information because it is making explicit an stated assumption in the argument--that is what's happening here. If you negate A it would say: even without screening (the same screening you are arguing for due to cost saving effects!) if would be cheaper to simply treat the patients....so the screening is so prohibitively expensive it would make more sense just to treat the patient once they got sick. Yeah, this would go completely against the argument so it clearly is the right answer.

B on the other hand just does not do anything for me. Ok so this is kind of like the first sentence but it kicks it up a notch to say it's most diseases not just some/certain diseases. Ok, so that goes way beyond what the argument assumes. We also need way more info here--which diseases are preventable? What's if some of these genetic flaws are preventable but do not require any treatment once the person gets a disease (say something like eczema is preventable and genetic, but once you get it a mild version where it's just itchy and it doesn't really affect your life...speaking from experience here)? Again just because a bunch of these are preventable or not preventable tells you nothing about which diseases can be cost effective if you prevent them. What if the argument simply needs one disease that is so expensive to treat that if we prevented it we could save money on it (look again at how mild the first sentence is), in that case the number of these diseases would not affect the argument because the argument does not tell us anything about the types of preventable diseases or the variety in costs of treatment as relative to prevention or anything else that would make B something that is assumed by the argument.