#23 - "DNA fingerprinting" is a recently-introduced

[biskam]

confused as to how this is a #% question. I chose A but now see the C is correct because it weakens the proponents' assumption that there's independence btw different characteristics. C is saying that in fact the characteristics are shared and maybe not independent?

But I still can't see why A is wrong... maybe on the grounds that it brings in outside info such as "other animals"

Thank you!

[nicholaspavic]

Hi biskam,

With Answer Option (A), if the shared material is not included in the procedure, then that would mean that the patterns are still independent. With this numbers and percentages question, you are asked to weaken the assumption that there is independence between the different characteristics represented by a single pattern. Answer (C) does precisely this by showing there are shared characteristics and therefore, they are not all independent of one another. In other words, it is reducing the overall amount of numbers or percentage.

Thanks so much for the great question and I hope this helps!

[cgb]

Hey can you please explain why it is C and not E? I was stuck on this question for a little bit.

Hi biskam,

With Answer Option (A), if the shared material is not included in the procedure, then that would mean that the patterns are still independent. With this numbers and percentages question, you are asked to weaken the assumption that there is independence between the different characteristics represented by a single pattern. Answer (C) does precisely this by showing there are shared characteristics and therefore, they are not all independent of one another. In other words, it is reducing the overall amount of numbers or percentage.

Thanks so much for the great question and I hope this helps!

[Christen Hammock]

Hi Cbg!

The only thing Answer Choice (E) tells us is that certain genetic diseases are, well, genetic—they appear in members of the same family because they're passed on through genes.

The author tells us that proponents of DNA fingerprinting assume that different characteristics are independent of one another. This means that individual DNA characteristics don't influence one another. If traits are independent, the more traits you consider, the less likely you are to find a complete "match." For example, it might not be so hard to find a person who matches one trait (like finding two people with blue eyes), but it becomes progressively harder to find someone with multiple matching traits (like blue eyes, red hair, tall, etc.). Having a certain genetic disease might be quite rare, and (E) doesn't give us any indication that genetic diseases increase the dependence between certain traits.

Answer Choice (C), on the other hand, directly challenges the assumption that the proponents make. If there are "various subgroups" in the population that share certain sets of genetic characteristics, that means that traits are dependent on one another. For example, if having blue eyes makes it more likely that you also have red hair, then matching this additional characteristic doesn't actually increase the odds of finding the right person.

[LSAT2020]

I am having a really hard time understanding the stimulus for this question, and thus am struggling to see how C is the answer choice. I must also note that I struggle hard core when it comes to analyzing a stimulus that is science based. Also, the stimulus gives us the assumption that supporters are making in order to push through their claim that DNA fingerprints are the way to go, which threw me off. Would greatly appreciate it if someone could try to explain the stimulus in more simple terms. Thanks in advance!

[Jeremy Press]

Hi LSAT2020!

To break this down to its essence, start with what the question stem wants: some fact that weakens the proponents' claim. What is their claim? That there are "astronomically high odds against obtaining a [DNA] match by chance alone." I don't have enough expertise to know the facts that will dent that kind of claim, so the test-makers give me an out: they tell me an assumption of the proponents' claim! What's the assumption? "[T]here is independence between the different characteristics represented by a single [pattern." You can always attack an argument by undermining its assumptions. So one good way to weaken the proponents' claim is to find a fact that shows there is NOT (or at least that there is unlikely to be) independence between these [genetically driven] characteristics.

Now's where we get into the nitty gritty (and the difficulty of certain LSAT questions). What is "independence" among...characteristics (or things, or phenomena, or really anything)? It means there's not some kind of necessary relationship among those things. It means that if we look out into the world, we shouldn't see much in the way of statistical patterns of association among those things. Why? Because if two things were necessarily connected (were dependent), then we should expect to find them together in a statistically significant way! So what am I looking for? An answer that suggests these characteristics are not independent: an answer that suggests we find those characteristics together in some kind of statistically significant way.

What's the only answer that does that? Answer choice C--it talks about the characteristics we're concerned with, and it raises the possibility that they're connected in a significant way (they're shared among certain population subgroups).

That's probably the shortest line to our answer choice. It definitely depends on recognizing (and this is your takeaway for future questions) that if two things are independent, then we shouldn't find them associated (in the real world) in statistically significant ways. Hold on to that thought for future questions!

I hope this helps!

Jeremy

[LSAT2020]

Hi LSAT2020!

To break this down to its essence, start with what the question stem wants: some fact that weakens the proponents' claim. What is their claim? That there are "astronomically high odds against obtaining a [DNA] match by chance alone." I don't have enough expertise to know the facts that will dent that kind of claim, so the test-makers give me an out: they tell me an assumption of the proponents' claim! What's the assumption? "[T]here is independence between the different characteristics represented by a single [pattern." You can always attack an argument by undermining its assumptions. So one good way to weaken the proponents' claim is to find a fact that shows there is NOT (or at least that there is unlikely to be) independence between these [genetically drive] characteristics.

Now's where we get into the nitty gritty (and the difficulty of certain LSAT questions). What is "independence" among...characteristics (or things, or phenomena, or really anything)? It means there's not some kind of necessary relationship among those things. It means that if we look out into the world, we shouldn't see much in the way of statistical patterns of association among those things. Why? Because if two things were necessarily connected (were dependent), then we should expect to find them together in a statistically significant way! So what am I looking for? An answer that suggests these characteristics are not independent: an answer that suggests we find those characteristics together in some kind of statistically significant way.

What's the only answer that does that? Answer choice C--it talks about the characteristics we're concerned with, and it raises the possibility that they're connected in a significant way (they're shared among certain population subgroups).

That's probably the shortest line to our answer choice. It definitely depends on recognizing (and this is your takeaway for future questions) that if two things are independent, then we shouldn't find them associated (in the real world) in statistically significant ways. Hold on to that thought for future questions!

I hope this helps!

Jeremy

I appreciate you taking the time to write out this detailed explanation. I will definitely be making note of the takeaway. Thank you so much!!!