Q11 - Sharks have a higher

[mcrittell]

Can someone walk me through this problem--and give me some additional advice on Inference questions. I don't know why but I always trip up on Inference questions such as this one.

[timmydoeslsat]

Sure thing.

This is a must be false question. This is a high standard to prove that something must be false.

These are a set of statements. There is no argument here.

The first statement tells us that sharks have a higher ratio of cartilage mass to body mass than any other organism.

An answer choice could play on this idea by giving us something like "Animal X has the same c mass to b mass ratio as sharks."

We would know that must be false because this statement tells us that sharks have a higher ratio than any other, so another organism could not have the same.

The next statement in the stimulus is that they have a greater resistance to cancer than any other organism.

This is the same concept here.

We could not have a situation where another organism is either more resistant to cancer or has the resistance to cancer as sharks.

The rest of the stimulus talks about how shark cartilage has a substance that stops tumor growth by halting a new blood network. In the past two decades, no responses among terminal cancer patients has been more positive than the response from those who consumed shark cartilage.

Same idea at play. We could not have a situation where a terminal cancer patient had the same or better response with a difference therapeutic measure than shark cartilage.

Answer choices:

A) Some resist cancer as well as sharks? NO WAY! The stimulus says that sharks have a greater resistance than any other organism!

That must be false, that is our answer.

Other answer choices:

B) Do not know which organism is most susceptible to cancer and its cartilage make up. Stimulus does not address this so it could be true.

C) This could be found in most organisms. The stimulus did not tell us that this could not happen. I believe it would have to be true that the other organisms would have to contain LESS of that substance. Of course, I am assuming that the substance in sharks that functions a certain way would in fact function in the same fashion and at the same success rate as that of sharks.

D) The terminal cancer patients can improve dramatically following other sorts of therapies. They just cannot improve more than those using shark cartilage. For example, therapy X causes 97% dramatic improvement, that means that shark cartilage would be an improvement of more than 97%. So it could be true that these patients experience dramatic improvements without the shark cartilage.

E) Sure, those organisms may have more efficient immune systems than sharks. Immune systems are not mentioned in this stimulus.

[mcrittell]

Is something definitely "could be true" if the passage doesn't mention it?

Also, Timmy, do you have any general advice on Inference questions? I always seem to tense up when it comes to Inference questions. I start to read robotically because I know it must be found in the passage, but it's to my detriment. Ideas?

[timmydoeslsat]

Yes, something could be true if it is not mentioned in the passage.

You will learn to love inference questions. Here are common templates for inference questions.

Stimulus will give you:

A ---> B

What must be false?

A ---> ~B

If the stimulus gave you if a then b, we know that every single time we have a, we must have b. The test writers may also play upon the contrapositive of that idea.

~ B ---> ~ A

Having a situation where B does not occur but A occurs is saying the exact same thing as before. Having a situation where A would occur without B.


Other common templates:

Something like you just saw on this problem. Greatest is mentioned for a variable, yet the answer choices of a must be false question would have something else equal it or surpass it.

On must be true questions, you are looking for something that is absolutely provable based on the stimulus.

Off of the top of my head, I can think of some situations.

B is required for A to happen. When B happens, then C does not happen.

We can diagram that statement as:

A ---> B ---> ~ C

We can then infer that A leads to ~ C. That is something that must be true.

The other answer choices may attempt to trick you by giving you answer choices like:

~C ---> A

or

~C ---> B

Those things are not necessarily true or false. Those statements are simply things that we cannot infer.

I would love to help further if you want to get to the more specifics.

[mcrittell]

Are a lot of inference questions formal logic-based? I feel that when I get to inference questions, I tend to over read them, mostly because I feel like most of the correct answer choices come out of nowhere. Obviously this can't be true.

[timmydoeslsat]

Yes, a lot of them are.

I often see the question stem of "If the previous statements are true, which one of the following MUST be true?"

These inference questions test concepts of formal logic like we discussed and, as you saw in this problem, issues with things like fastest, greatest, etc.

If there is another inference question you would like to go over, post it up and I will go through it with you.

[mishawakajess]

I understand why A is correct, however, I don't understand why B cannot also be false (and a correct answer). If we are to take "susceptible to cancer" as the opposite of being resistant to cancer, then isn't it true that all other non-shark organisms (including those most susceptible to cancer, which the stimulus tells us *excludes* sharks, since sharks have the most resistance to cancer) necessarily have a lower percentage of cartilage than "some organisms that are less susceptible to cancer", i.e., sharks (because sharks are necessarily less susceptible to cancer than the organism that is the most susceptible to cancer)?

It seems to me that B is saying: [any-non shark organism] has a higher percentage of cartilage than [sharks]. This is not true since sharks have the most resistance to cancer.

I think I am misunderstanding something and I don't know what it is. Is it unfair to correlate/equate susceptibility to cancer with resistance to cancer? I suppose an organism could conceivably have cells that are most likely to turn cancerous but at the same time have these substances that inhibit tumor growth, but it seems more plausible that LSAC used susceptibility to cancer as a paraphrase of the concept of resistance to cancer.

Please help!