#18 - In experiments in which certain kinds of bacteria were

[Dave Killoran]

Hi LSATNoobie,

Let me go backward here. First, the conclusion of "None" means that there is no conclusion that can be drawn. Literally, we don't know anything from combining the two prior statements. I'll go back and change that wording so it's clearer

Second, the problem with answer choice (C) is that it doesn't work, so we are looking at a combination that is flawed. That makes the analysis more tricky, because you're showing the failure of (C) and why it doesn't produce the conclusion in the stimulus. So let's walk through it once more and try to make it clearer.

Basically, you have a Justify question, so to see if the answer works, you have to have pass through the Justify Formula:

• Premises + Answer Choice = Conclusion
  
  And just for reference:
  
  • Premise: [some] genetic mutation is random
    Correct answer: ?
    Conclusion: all genetic mutation is random
    
    Now, we need the right answer to combine with the premise to force the conclusion.

So let’s apply that to (C):

• Premise in this problem: “[some] genetic mutations occurred at random in the populations.”
  
  Answer choice (C): “If all genetic mutations in bacteria are random, then all genetic mutations in every other life form are random also.”

The resulting conclusion from combining the two above: there is no valid conclusion that can be drawn. It’s an “if” statement in the answer choice, and we don’t know that we have the sufficient condition activated because "some" isn't enough to make that happen. So, we can't draw the conclusion made in the stimulus, and this answer fails to make the Formula work.

I tried to use an example that mirrors that with my football players example:

• Premise in this problem: “Some high school football players are athletic.”
  
  Answer choice (C): “If all high school football players are athletic, then football players at every level of the sport are athletic.”
  
  Conclusion: there is no valid conclusion that can be drawn

Let me try a different example, that gets to the heart of the issue without following the exact form of the argument the way I did with my example. In this case, I'll use rich or poor as the basis just to keep it simple:

• Stimulus: Some of us are rich, therefore all of us are rich.
  
  Answer choice (A): Either all of us are rich or none of us are rich.
  Answer choice (C): If All of us are rich, then the whole world is rich (this is imperfect, but let's go with it)

Now run each through the formula just to see how it works:

• Answer choice (A)
  
  Premise: Some of us are rich.
  Answer choice (A): Either all of us are rich or none of us are rich.
  
  Conclusion: All of us are rich

Ok, perfect, that worked. When we combined the answer choice with the premise, it produced the same conclusion as in the stimulus. This is the correct answer!

• Answer choice (C)
  
  Premise: Some of us are rich.
  Answer choice (C): If all of us are rich, then the whole world is rich.
  
  Conclusion: No conclusion can be drawn.

We only know that some of us are rich, but the sufficient condition in the answer is "all," and we don't know that for sure. so, the sufficient isn't activated, and we can't draw any absolute conclusion. Thus, this answer does not produce the same conclusion as in the stimulus.

Please let me know if that helps. Thanks!

[lsatnoobie]

That was the best answer I have ever received for any question I have ever asked in life. Thank you so much haha.

[mrcheese]

Exactly. (C) is a brilliant answer because it contains the element you want to produce, but it contains it in a manner that doesn't allow you to produce that result.

Make sure you understand this question perfectly—it is one of my all-time favorites for understanding how the whole Justify idea works on this test!

I see what you are saying. It definitely illustrates the point.

I feel like I actually learned something profound when I came across this question. I got it wrong - A and C were the contenders.

[ridolph.lauren]

In regard to the leap from "some" in the premise to "all" in the conclusion that David speaks of when explaining this question, is it safe to say that this a common occurrence in these "Justify the Conclusion" questions and therefore, we should be consistently looking for this leap in order to fill in the missing gap with the correct answer choice?

[ridolph.lauren]

Hey again, noobie! What Dave meant in that response with the football analogy was that no conclusion could be drawn based on the premise (some h.s. football players are athletic) plus the answer choice (if all are, then all football payers at all levels are). The reason we cannot draw any conclusion there is because we don't know if ALL h.s. players are athletic - we only know that SOME are! That's the same issue as the one in the argument plus answer choice C: we cannot conclude anything based on the premise (some mutations were random - the ones in this bacteria in this one experiment) plus answer C (IF all bacterial mutations are random then all mutations everywhere are random) because we don't KNOW that all bacterial mutations are random. We only know that SOME are (these ones, from this experiment).

The correct answer justifies the conclusion because it adds the information that there are only two choices - all or none. We know from the premise that it is NOT "none", because we got some. If it isn't "none", and it must be either all or none, then it MUST be "all"! That was our conclusion, and this weird, counter-intuitive, incredibly unrealistic and very strong answer justifies it.

That's a common thread in many justify questions, btw - the answer choices tend to be very powerful, with extreme claims and extreme language. Hey, we are trying to PROVE something, not just strengthen it, so the more extreme the better, usually, right? The exception to that is when they ask which answer is REQUIRED to justify the conclusion. In that case, you want the answer that justifies the conclusion without going overboard, and an overly strong answer is probably incorrect. Watch out for those!

Let us know if that clears things up for you!

So based on your explanation of the answer, if Answer A had said something like "Both, all genetic mutations are random and none are random", that would make it incorrect because "none" was taken out when the "some" was applied to the mutations being random. The use of the word "or" in Answer choice A is what allows it to be correct simply because the "all" is included in the choice?

[Robert Carroll]

ridolph.lauren,

Dave's post in this thread on closing the gap in language is just an instance of the Mechanistic Approach to Justify questions - it always works, although it's not always the easiest or most straightforward way to do Justify questions, so, yes, this is a very common occurrence for Justify questions.

"Both, all genetic mutations are random and none are random" wouldn't make sense as an answer choice, because it would be conjoining two contrary statements.

Robert Carroll

[ridolph.lauren]

ridolph.lauren,

Dave's post in this thread on closing the gap in language is just an instance of the Mechanistic Approach to Justify questions - it always works, although it's not always the easiest or most straightforward way to do Justify questions, so, yes, this is a very common occurrence for Justify questions.

"Both, all genetic mutations are random and none are random" wouldn't make sense as an answer choice, because it would be conjoining two contrary statements.

Robert Carroll

Robert,

True, that example would make it way too easy to eliminate. I guess I was just trying to come up with something to compare that answer with one that would be wrong. The "or" in it is what confuses because part of it is correct and the other part isn't. So I guess my question is, because part of the answer is correct and the answer itself gives a choice (by the use of "or"), is that what makes that answer sufficient enough to justify the conclusion?

Thank you in advance,

Lauren

[Adam Tyson]

You're close there, Lauren, but it's more like the answer gives you only two options, and the stimulus proves that one of those options is not possible, so the other option (the one given in the conclusion) is the only one available. For example:

I had only two choices for my dinner tonight - fish or chicken.

I ate dinner, and it wasn't fish.

Thus, I must have had chicken.

Just like in the argument, something happened (I ate dinner and it wasn't fish = there were some random mutations in the bacteria), and the conclusion was absolutely certain about what that proved (I had chicken = all mutations are random). The correct answer supplied the two options and indicates that those are the ONLY options (fish or chicken = all or none).

So it isn't so much the "or" that makes that answer sufficient, but the fact that the answer eliminates every other possibility. It's the certainty that it can ONLY be one or the other that does the job.

[olenka.ballena@macaulay.cuny.edu]

Hi Powerscore,

Now that I've read through this whole thread, I understand why A is correct (connecting the leap between some and all). However, what threw me off was that I thought that according to the mechanistic approach, if a term is in both the premise and conclusion (genetic mutation), then it most likely won't appear in the correct answer choice. Based on that, I eliminated C & D. I ultimately chose B because I thought that if the bacteria they tested were extremely common, then they are a strong representative of all the bacteria, and thus if the genetic mutations occurred with bacteria that is extremely common, then it supports the conclusion that all genetic mutation is random.

In other words, I did kind of see B as bridging the gap between some and all, but in retrospect I can see how A is stronger. However, I would like to gain some more clarity as to why B is wrong. If the experiment with extremely common bacteria showed that some genetic mutations are random, then because the bacteria is very common, then wouldn't it support that all (or most) genetic mutation is random? Would this be more of a strengthen answer choice rather than a justify question? Thanks in advance!

[Adam Tyson]

It's not that a common term CANNOT be in the answer, Olenka, but that it may not NEED to be. In this case, to close the gap between the premises (we got some random mutations) and the conclusion (all are random), we need to link "some" to "all." It's okay if they mention genetic mutations just to give the answer some scope and meaning.

But "common" doesn't mean "all"! As you've said, that could just mean "most," and so that does NOT justify the conclusion about all. It's just not strong enough!