#3 - A recent study involved feeding a high-salt diet to a

[Administrator]

Complete Question Explanation

Evaluate the Argument—#%. The correct answer choice is (D)

The author of this stimulus presents an experiment in which a rat colony is fed a high-salt diet, after which the rats are tested for high blood pressure. Based on the fact that significant numbers of rats had varying degrees of high blood pressure afterwards, the conclusion of the stimulus is that there is a causal link between high salt intake and high blood pressure.

We might note the problem with this assessment: while it’s true that many of the rats had high blood pressure after the experiment, we have no basis for comparison without information about their health before the experiment. Thus we should perhaps seek the answer choice which deals with the topic of some basis for comparison.

Correct answer choice (D) presents our prephrase from above in question form: we need to know how much of the population was already afflicted in order to draw any logical causal conclusions linking high salt intake with high blood pressure in rats. Applying the Variance Test to confirm this answer, the lower the number of rats with high blood pressure at the outset, the more believable the asserted causal link is.

[lsatstudier]

Hi,

I was wondering if someone could explain how to prephrase these types of questions. Or, maybe you don't have to? I identified the conclusion in the stimulus but then felt kind of lost when I got to the answer choices.

Any advice would be great! Also, any suggestions for dealing with #% questions?

Thank you so much in advance!

[Adam Tyson]

You're welcome, studier!

This is an Evaluate the Argument question, a fairly rare type (although on one recent test there were two of them, a lot more than normal). It's a hybrid between a Weaken and a Strengthen, where the correct answer is itself a question, and the two opposing answers to that question will have opposite effects on the argument. One answer will strengthen the argument, the opposite answer will weaken it.

I prephrase these questions by asking myself "what do I want to know?" I see that there is a problem in the argument, something missing, and I ask myself what would help and what would hurt, and then my prephrase is a question the answer to which will tell me which situation is in place. That's the thing I want to know.

Here's a simple example: "All dogs are mammals, so Fido must be a mammal." Now, what do you want to know to determine whether my conclusion is good or not? What I want to know is whether Fido is a dog. If he is, the argument is good, and if he isn't, the argument is bad. That's the process for prephrasing Evaluate answers - figure out what the thing is that you need to know.

Give that a try and see if it works for you. Good luck!

[mandrewg]

Hi PS Team,

Was curious if I could get an explanation as to why Answer Choice A is incorrect? Many thanks in advance!

[Adam Tyson]

Let's apply the appropriate test to that answer and see, mandrewg! First, let's try "a lot more" - there was a lot more salt in the high salt diet than in the normal diet. Does that strengthen the claim that the high salt diet had something to do with high blood pressure? Nope - we still don't know if there is any connection, because we don't know what the "baseline" blood pressure was in these rats, before the study began. We can't know if it changed any as a result of all that extra salt. For the same reason, this answer does nothing to weaken the argument either. Without knowing about whether their BP changed, this answer just does nothing to the argument.

For that reason, we don't even need to think about the opposing answer, which would probably be "not any more salt than in a regular diet." But if we did consider that opposite answer, would it matter? Would that either hurt the argument, or else help it? The answer is still "no," because without knowing what their BP was like on a lower-salt diet we could not know anything about whether the salt had any effect.

The correct answer to any Evaluate the Argument question has to pose a question. One answer to that question will strengthen the argument, while the opposite answer will weaken it. If either of the two answers to that question has no impact, or if the impact of that answer is unclear, then that answer choice is a loser! Both of the answer to the question raised in answer A leave us uncertain, and so it loses no matter which way we look at it.