#8 - Doctor: In three separate studies, researchers compared

[AJH]

^^ I am wondering the same thing. I chose E, but was also torn with D & A. Why would an additional study (like in A &E) be insufficient to weaken the argument? It seems like a study that discredits the study on which the argument is based would most weaken that argument.

[James Finch]

Hi AJH,

Answer choice (A) fails to weaken the conclusion because it only provides more evidence that night-lights don't cause nearsightedness at all; to weaken the argument, we must make it less likely that the nearsightedness caused by night-lights disappears with age. In order to do that, we need nightlights to cause some nearsightedness.

Answer choice (D) does the same as (A): it undermines the argument that night-lights cause nearsightedness. But we are looking to undermine the conclusion that the nearsightedness caused by night-lights disappears with age.

Answer choice (E) undermines that conclusion by studying even older children and tying some of the nearsighted ones to having night-lights as infants. This provides some evidence that any possible nearsightedness caused by night-lights doesn't disappear over time, as these children are even older than those in the other studies.

Hope this clears things up!

[HEIDIHAI2]

The most recent reply made by Powerscore is simply confusing. D is the correct answer while the reply is telling us why D isn't adequate. There has been much confusion over why E is wrong, and I was there too, but I have finally figured out why and I would like to share my reasoning.

E is wrong simply because the study described in E is not (necessarily) valid, and we know in LSAT we are looking for absolute proof. The fact that "several of the children who had slept with night-lights as infants were nearsighted" doesn't prove any correlation between sleeping with night-lights as infants and being nearsighted, because the result can be purely coincidental. First, the near-sightedness could be for other reasons, and second, we don't know if some of the children who did not sleep with night-lights as infants were also near-sighted. In a word, the study does not establish any concrete claim regarding the correlation between being near-sighted and sleeping with night-lights on as infants. It proves nothing.

I feel that most of us would have easily identified that this isn't a valid study, at least not so judging by the information given, had it been in the question stem. Because it is an answer choice, however, I somehow became less wary.

[Jennifer Janowsky]

Heidi,

I believe James' response was worded confusingly--he is not saying that (D) is incorrect. What he is saying specifically is that (D) and (A) both undermine the idea that night-lights cause nearsightedness. He is also saying that we are looking to undermine the conclusion that the nearsightedness caused by night-lights disappears with age, as well--which unlike (A), (D) does! This makes (D) the correct answer.

As far as (E) goes, you are correct that it doesn't establish correlation. Just because "several" of the children were nearsighted doesn't mean night-lights were the cause, and we also don't know how many children out of 100 "several" is. If half of the children slept with night lights and 10 of them were nearsighted, is that significant? What if 10 of the children without night-lights were, too? For these reasons, (E) isn't a good answer.

I hope that clears up the confusion!

[chian9010]

When I first read the stimulus, I found a flaw which I would expect to be the correct answer choice. However, it didn't appear.

For this question, I eliminate D because I don't think this is the correct reason to weaken the doctor's argument. The three studies focused on different groups of children (young children vs older children) and made a conclusion about "temporal" effect saying that the effect disappears with age. Doesn't anyone feel weird? How can the author make temporal conclusion by comparing different groups. He/she should focus on one group of children and do a temporal experiment.

This question reminds me of another LSAT LR question (I forgot from which preptest) but the stimulus is describing as doing a survey asking about financial income from a wide variety of people. The survey found that young people (<30) are more willing to talk about their financial income than old people (>65). Therefore, the author concluded that as people aging, they become more and more unwilling to talk about their financial income. something like that. And the flaw is that the temporal conclusion cannot be made simply from two different groups. I feel this question is exactly the same!

Therefore, I eliminate D because the problem is not about enough children but because temporal conclusion cannot be made from two different groups of samples.

I understand why A and E are not correct because whether the two results are true or not do not affect the causal relation.
However, I don't think D is correct neither and would like to know if anyone has the same problem as I do.

[Brook Miscoski]

Chian,

What you are talking about is a longitudinal study (the same group is followed over time). It is not correct that longitudinal studies are the only way to make an inference about whether any effects of night lights dissipate over time. If you have large enough sample sizes of people at different ages, it may still be possible to make valid inferences about whether the effects of night lights on sight dissipate over time. Thus (D) does illustrate a problem with the doctor's claim--if the two later studies did not examine enough children, he could not make the inference he seeks.

Without looking at that other question you mention, it's not possible for me to determine how that question is contributing to your analysis of this question or to offer a correction. However, if you would find the question and cite it specifically, that can be addressed by myself or someone else.

[lsatstudying11]

Hello,

I have a question about how we should be approaching this question and the conclusion from the start. Is it fair to say that, after reading the conclusion, we should or could identify our goal and focus to be weakening the idea that the effects goes away with age? I guess I am wondering if it would make sense to, from the beginning, forget about the question of whether nightlights cause nearsightedness, since the conclusion has the 'if'? And, in turn, could we have used this idea to get rid of A, B, C, and E (although E kinda gets at it but not really/its too weak) since they lack that change over time focus?

Thanks so much for your help

[Adam Tyson]

That's exactly how I would go about it, lsatstudying11! The conclusion is conditional, so the author isn't really invested in whether nighlights cause nearsightedness, but only whether the effect, if there is one, goes away with age. Attacking the validity of the second study is a great way to go about doing that! Good job sorting through the losers to find the only answer worth considering!

[limersereau@gmail.com]

Hi all,

I understand why D is the correct answer and that it is the best answer of the bunch. Nonetheless, can someone explain why E is incorrect? I felt that it clearly attacked the conclusion.

Thank you!

[Paul Popa]

Hey Lime,

I'd be happy to help with that! There are two major problems I see with (E). The first is age. While the older age of the students in the fourth study might seem to weaken the conclusion at first, it actually opens up a can of worms. The older a child is, the more possible causes of nearsightedness they might have been exposed to in life at this point. We can't say for sure that the use of a night-light as an infant is what led to the nearsightedness for each of those who experience it.

In addition, "several" is not actually strong enough to deduce a real correlation. "Several" can be any amount from 7 to 17 to 70--this term alone is not helpful to deduce anything. Now, if the answer choice had said "most," this is a 50%+1, and it does a better job of indicating a positive correlation between night-light use in infancy and nearsightedness in childhood. Hope this helps!