Q17 - Reporter: A team of scientists

[sgorginian]

I quickly picked B as my answer (correct answer) but then changed my answer when I got to D.

(B) made sense because essentially it is saying "hey, even if you get some false positives, and if you are one of those that are falsely positive, you at least have treatment decisions to look into"

Then I saw (D) which made most sense to me. In my head I was saying...."gee...I hope those two kids that were falsely positive won't get treatment because it might hurt them since they aren't really autistic." and BAM that's what answer choice (D) says....those children incorrectly identified will not be affected by the treatment aimed at helping austic children".

So, simply put, why is D wrong? Thank you!

[sgorginian]

After another look at my core, here is what I have.

New test correctly diagnosed 10/16000 correctly for autism and 2/16000 incorrectly sooner than before. ==================> so, autistic kids can now benefit much earlier than before with treatment.


Is answer choice D wrong because it introduced something that doesn't fill the gap? After another look, I feel answer choice D is a general emotional response, that is relevant in real life, but not in LSAT life. Meaning, that (D) really doesn't bridge the gap.

Am I correct? I am not sure....

[giladedelman]

You are correct! You've hit the nail on the head!

So, since this is an assumption question, you were right to start by identifying the core:

New test correctly diagnosed 10/16000 correctly for autism and 2/16000 incorrectly sooner than before. ==================> so, autistic kids can now benefit much earlier than before with treatment.

And, as you said, we're looking for an answer that fills the gap.

(B) is correct. We need to assume that a test that sometimes gives false positives can provide a reasonable basis for treatment decisions. If this weren't the case, then we couldn't conclude that the test would help autistic children get treatment earlier in life.

(A) is incorrect, attacking information that the argument presents as fact: we're told that this is the first test that diagnoses children as young as 18 months old.

(C) is out of scope. We don't really care if the test can be used on all children; we care about what we're told, which is that it correctly identifies the autistic children tested, and gives some false positives.

(D) is out of scope. Like you said, it's very tempting -- what about those poor children who are wrongly diagnosed -- but ultimately it has nothing to do with the argument! That is, whether these children are adversely affected in no way impacts our conclusion that the test will help autistic children.

(E) is out of scope. It doesn't matter whether there was evidence that autism affected young children before the advent of this test.

Does that clear everything up for you? Again, you got it quite right: (D) is a type of real-world reaction that, sadly, has no place in LSAT-land.

[farhadshekib]

You are correct! You've hit the nail on the head!

So, since this is an assumption question, you were right to start by identifying the core:

New test correctly diagnosed 10/16000 correctly for autism and 2/16000 incorrectly sooner than before. ==================> so, autistic kids can now benefit much earlier than before with treatment.

And, as you said, we're looking for an answer that fills the gap.

(B) is correct. We need to assume that a test that sometimes gives false positives can provide a reasonable basis for treatment decisions. If this weren't the case, then we couldn't conclude that the test would help autistic children get treatment earlier in life.

(A) is incorrect, attacking information that the argument presents as fact: we're told that this is the first test that diagnoses children as young as 18 months old.

(C) is out of scope. We don't really care if the test can be used on all children; we care about what we're told, which is that it correctly identifies the autistic children tested, and gives some false positives.

(D) is out of scope. Like you said, it's very tempting -- what about those poor children who are wrongly diagnosed -- but ultimately it has nothing to do with the argument! That is, whether these children are adversely affected in no way impacts our conclusion that the test will help autistic children.

(E) is out of scope. It doesn't matter whether there was evidence that autism affected young children before the advent of this test.

Does that clear everything up for you? Again, you got it quite right: (D) is a type of real-world reaction that, sadly, has no place in LSAT-land.

I think (A) is incorrect for another reason:

We are told that scientists devised a new test that for the first ACCURATELY diagnoses autism in children as young as 18 months old.

A states - "No test INTENDED for diagnosing autism at such an early age existed before the new test was devised".

The argument does not need to assume (A).

For all we know, there could of been several tests intended to diagnose autism in children as young as 18 months old before the new test.

However, these previous tests, if they existed, need to be all failures for the argument to work.

[mitrakhanom1]

i dont understand why the children who were wrongly identified as autistic are not included as "autistic children" in the conclusion,"autistic children can therefore now benefit much earlier in life than before from the treatments already available." Which is why i don't understand why D is the wrong answer. I put D because I felt that those children who are wrongly identified as autistic won't be negatively affected by the treatments is the assumption being made between the premise and the conclusion. I fail to see how answer C is justified as being the correct answer.

[tommywallach]

Hey Mitrak,

First off, the answer is (B), not (C), which might help. We need to know that the fact this test occasionally screws up doesn't make it useless.

As for (D), it's actually irrelevant. Our conclusion is:

Autistic children can benefit much earlier in life from treatment.

Our conclusion has nothing to do with kids who aren't autistic. What you did was you changed the conclusion in your head to something like this:

The test is, on the whole, a good thing.

Now, we would care about how non-autistic children are being affected.

Hope that helps!

-t

[uhdang]

While I have a specific question regarding B), I want to share my thought process as well.

First of all, the Core:

Among 16,000 young kids, new test successfully diagnosed 10 autisms and wrongly diagnosed 2. ==> Autistic children can benefit much earlier than before.

This argument assumes that this test will still be beneficial for autistic children despite it's faulty identification. And B) correctly points out this assumption.

First of all, let's go through incorrect answer A), C), E)

A) This is a premise booster. This is just strengthening the very first sentence.

C) Whether this test can be used to evaluate children on their development of verbal skills or not is not necessary to reach the conclusion. We are concerned with whether this test can benefit Autistic children in earlier in life now or not. Out of scope.

E) Validity with evidence is not what we're dealing with. This might show that this test is revolutionary, but has no influence on the bridge. Out of scope.

Finally, B) and D)

I had to fight over B) and D) as well, and chose D) first and got it wrong. And later figured out that conclusion only concerns with "autistic children", so talking about those falsely identified children is out of scope, irrelevant.

So, going back to my original thought on B), I originally crossed this out because I thought this sounded more like "sufficient assumption" than "necessary assumption", because it talks about "a diagnostic test" in general rather than the New Test this question is dealing with. So, I thought that this not only bridges the gap but does some more.

And then I tried applying negation technique, and it DOES destroy the argument. So, I was really confused with it... And then I remembered when I was drilling "assumption identification" from Manhattan Logical Reasoning, that there are some arguments that can both have "necessary" AND "sufficient" assumption.

So, I was wondering if this is the case with B)? If it is so, could anyone elaborate on this case a bit?

[uhdang]

I went back and looked for an example with both "necessary" and "sufficient" assumption. I just changed a bit of words and numbers from what I found. Here it goes:

A computer costs $200 dollars, so Kevin has enough money in his pocket.

An assumption that could both be "necessary" and "sufficient" would be, Kevin has at least $200 dollars.

This would sufficiently bridge the premise and conclusion, while it is also necessary (negating it would say, "Kevin does NOT have $200 dollars).

This example deals with numbers, so it seemed easier to spot, but although I am almost certain that answer choice B) is both necessary and sufficient, I want to hear what others say.

[Last_lsat]

In B) "A diagnosis test .... can still provide..", "can" make it the general " a diagnosis test" apply to this specific test. "Can" actually make it more general, the same as "at least", is a typical "necessary" answer. It is like "at least $100" in your next example, is not sufficient, but necessary.

[uhdang]

Thanks for the reply. I've been wishing to see what other people think of this.

In B) "A diagnosis test .... can still provide..", "can" make it the general " a diagnosis test" apply to this specific test. "Can" actually make it more general, the same as "at least", is a typical "necessary" answer. It is like "at least $100" in your next example, is not sufficient, but necessary.

Two things,

1) Where do we learn that "a diagnostic test that sometimes falsely gives a positive diagnosis" is referring to this specific test? Since it didn't use any indicating words like "this" or "the" or "the diagnostic test from this experiment", or else, it could just as well be including, or be applied, to other possible diagnostic tests that sometimes falsely gives a positive diagnosis. Thus, making it a general statement that bridges the gap and more by covering other cases as well -- what sufficient assumption does.

2) Now that I think about it, (thanks for pointing out "can" for me) this "CAN" actually makes the statement "less" general and makes this statement NOT a sufficient statement. If B) were to just say, "A diagnostic test that sometimes falsely gives a positive diagnosis still provide a reasonable basis for treatment decisions" (without "can"), then it would be stronger and more general, so this would ABSOLUTELY make sure that the gap between the premise and conclusion in stimulus has been filled and cover other extra cases that also "sometimes falsely gives a positive diagnosis." HOWEVER, since "can" creates a possibly-NOT scenario where that particular test might not still provide a reasonable basis, this statement sounds less general and good enough to say that it's necessary assumption (but not strong enough to be sufficient assumption).

I can definitely see that "can" contributes to making this statement "necessary", but still not so clear about it, though. If you or anyone can elaborate on this "can-necessary assumption" issue, I would appreciate it.

P.S. I would also appreciate verifying / feedback on my thought above.

[ohthatpatrick]

Great questions and follow-ups.

---- I find the notion of "Necessary AND Sufficient" to be pretty useless on LSAT. There technically can be such an idea, as our books and you have noted, but I don't know if I've ever seen such an answer on the test. More importantly, it just has nothing to do with picking the right answer. You never need to know that something is both.

On Necessary Assumption, the correct answer must fulfill this function:
If false, it is very hurtful to the argument.

On Sufficient Assumption, the correct answer must fulfill this function:
If true, it guarantees the conclusion.

(B) would not be Sufficient, because (B) does not guarantee the truth of the conclusion.

Even if I say "this test is a reasonable basis for treatment decisions", you need to add in ideas like:
- people know the test exists
- people can afford the test
- people are willing to administer the test
- treatments already available are affordable
- the treatments already available can benefit children as young as 18 months old

Those are just the first handful of ideas that came to mind.

A sufficient assumption leaves no term undefined, no wiggle room whatsoever. That's why Sufficient Assumption questions are testing Missing Links (logic math) 98% of the time (the other 2% of the time, the correct answer rules out the ONE possible objection).

A sufficient assumption would be
"If a new test exists that can correctly diagnose children later confirmed to be autistic, then autistic children can now benefit much earlier in life than before from the treatments already available"

---- Correct answers on Necessary Assumption typically have weak or ruling-out language. Weak language consists of terms such as "some, may, might, can, at least, sometimes, not all, need not, not necessarily". Ruling-out language usually sounds like, "Doing such-and-such would NOT lead to ______".

---- You're allowed on LSAT to refer to something specific by using a broader category, as long as you're only claiming that "SOMETHING from that category has a certain trait."

For example,
Lucy is Ben's dog. Thus, Lucy is Ben's best friend.

A necessary assumption could be
(A) A nonhuman animal can be Ben's best friend.

There was no reason I had to choose the group "a nonhuman animal". The answer would still be correct if I said "an animal from the canine family" or "a placental mammal".

As long as "dogs" belong to the broader group "a nonhuman animal", then (A) is relevant to them.

As stated, (A) doesn't say much for sure about dogs. (Necessary assumptions are pretty weak on their own)

But negated, (A) disqualifies an entire category of things, which includes dogs.

negated (A) ---- a nonhuman animal CANNOT be Ben's best friend.

Similarly, when you read (B), you're just asking yourself, "WAS this a diagnostic test that sometimes gives a false positive? Yeah. Okay, then I should keep reading. It's relevant to the topic at hand."

And, as you saw, when you negate (B) it allows you to say that ALL false positive diagnostic tests are USELESS when it comes to making reasonable treatment decisions.

When I say "a nonhuman animal CAN be Ben's best friend", it might feel too broad, especially if you consider bad contenders for best friends:
a slug? a barnacle? an ant? a gnat?

But saying "a nonhuman animal CAN be Ben's best friend" is identical to saying "at least one nonhuman animal is capable of being Ben's best friend".

Hope this helps.

[uhdang]

Great questions and follow-ups.

---- I find the notion of "Necessary AND Sufficient" to be pretty useless on LSAT. There technically can be such an idea, as our books and you have noted, but I don't know if I've ever seen such an answer on the test. More importantly, it just has nothing to do with picking the right answer. You never need to know that something is both.

On Necessary Assumption, the correct answer must fulfill this function:
If false, it is very hurtful to the argument.

On Sufficient Assumption, the correct answer must fulfill this function:
If true, it guarantees the conclusion.

(B) would not be Sufficient, because (B) does not guarantee the truth of the conclusion.

Even if I say "this test is a reasonable basis for treatment decisions", you need to add in ideas like:
- people know the test exists
- people can afford the test
- people are willing to administer the test
- treatments already available are affordable
- the treatments already available can benefit children as young as 18 months old

Those are just the first handful of ideas that came to mind.

A sufficient assumption leaves no term undefined, no wiggle room whatsoever. That's why Sufficient Assumption questions are testing Missing Links (logic math) 98% of the time (the other 2% of the time, the correct answer rules out the ONE possible objection).

A sufficient assumption would be
"If a new test exists that can correctly diagnose children later confirmed to be autistic, then autistic children can now benefit much earlier in life than before from the treatments already available"

---- Correct answers on Necessary Assumption typically have weak or ruling-out language. Weak language consists of terms such as "some, may, might, can, at least, sometimes, not all, need not, not necessarily". Ruling-out language usually sounds like, "Doing such-and-such would NOT lead to ______".

---- You're allowed on LSAT to refer to something specific by using a broader category, as long as you're only claiming that "SOMETHING from that category has a certain trait."

For example,
Lucy is Ben's dog. Thus, Lucy is Ben's best friend.

A necessary assumption could be
(A) A nonhuman animal can be Ben's best friend.

There was no reason I had to choose the group "a nonhuman animal". The answer would still be correct if I said "an animal from the canine family" or "a placental mammal".

As long as "dogs" belong to the broader group "a nonhuman animal", then (A) is relevant to them.

As stated, (A) doesn't say much for sure about dogs. (Necessary assumptions are pretty weak on their own)

But negated, (A) disqualifies an entire category of things, which includes dogs.

negated (A) ---- a nonhuman animal CANNOT be Ben's best friend.

Similarly, when you read (B), you're just asking yourself, "WAS this a diagnostic test that sometimes gives a false positive? Yeah. Okay, then I should keep reading. It's relevant to the topic at hand."

And, as you saw, when you negate (B) it allows you to say that ALL false positive diagnostic tests are USELESS when it comes to making reasonable treatment decisions.

When I say "a nonhuman animal CAN be Ben's best friend", it might feel too broad, especially if you consider bad contenders for best friends:
a slug? a barnacle? an ant? a gnat?

But saying "a nonhuman animal CAN be Ben's best friend" is identical to saying "at least one nonhuman animal is capable of being Ben's best friend".

Hope this helps.

Thanks for clearing up, Patrick.
Now, I feel like I know what "CAN" does in assumption statement. This clears up two things for me:

1) No need to look for Necessary AND Sufficient assumption -- as long as I have a sufficient amount of knowledge on how to distinguish them and how they are different.
2) 'CAN' could play a big part in necessary assumption statement -- Your example at the end was very helpful: saying "a nonhuman animal CAN be Ben's best friend" is identical to saying "at least one nonhuman animal is capable of being Ben's best friend".

Just one more confirmation on this, though. In your example, while a nonhuman animal CAN be Ben's best friend is a necessary condition, would a nonhuman animal is Ben's best friend be a sufficient condition?

Thanks for the help as alway.

[sclw64]

“falsely gives a positive diagnosis”/"wrongly identified 2 children as autistic" . Do they mean the 2 children are actually not autistic? then choice B out of the scope?

[ohthatpatrick]

I'm not sure I understood your question, but when the argument says

"the test wrongly identified 2 children as autistic", that means that the children are NOT autistic, but the test said that they were.

This is known as a "false positive".

So this new test is "a diagnostic test that sometimes falsely gives a positive diagnosis".