#3 - Moore: Sunscreen lotions, which are designed to block

[Administrator]

Complete Question Explanation

Flaw in the Reasoning—CE. The correct answer choice is (E)

Moore’s argument considers how well sunscreen lotions block ultraviolet radiation, a cause of skin cancer. According to the many scientific studies Moore references, people who consistently use sunscreen get as many skin cancers as those people who use sunscreen rarely, if at all.

The problem with Moore’s argument is that it does not provide us with enough information about the people who were the subjects of the study. What is their biological predisposition to developing skin cancer? Where do they live? How much time do they spend in the sun? All of these questions point to the concern that we have with all causal arguments on the LSAT: the stimulus authors assume there is just one potential cause for each effect. Bolstering our view of this error is that we already know that there is a behavioral difference between the people mentioned in the stimulus. Why is it that some of the people use sunscreen regularly while the others do not? We cannot simply assume that these people are exactly the same in every other way that is relevant to the conclusion, but that is what the author of the stimulus appears to do.

This is a Flaw in the Reasoning question. Our prephrase is that the correct answer choice will describe the author’s assumption that there is nothing besides the poor performance of sunscreen lotions that causes the difference in the occurrence of skin cancer described in the stimulus.

Answer choice (A): The argument does not take other possible health benefits of sunscreen lotion for granted. We know this because other potential health benefits of the lotion are irrelevant to the conclusion.

Answer choice (B): There is no indication from the stimulus that it is necessary to distinguish between the number of cases and the severity of those cases. The occurrence of skin cancer at all, if caused by exposure to ultraviolet radiation, would indicate that the radiation was not blocked by the sunscreen lotion.

Answer choice (C): Those sunscreen lotions that are not designed to block ultraviolet radiation are irrelevant to the conclusion.

Answer choice (D): This answer choice is incorrect because there is no reason to think that evidence relied on by Moore would be impossible to challenge.

Answer choice (E): This is the correct answer choice because it points out that Moore has failed to address a possible alternate cause for the development of skin cancer suggested by the stimulus: perhaps the people who do not wear sunscreen lotions as frequently do not need the same level of protection because they do not go out into the sun as frequently as those who wear sunscreen lotion more often. If they do not go out into the sun as frequently, then they would have a lower risk of developing skin cancer caused by exposure to ultraviolet radiation, with or without the benefit of sunscreen lotion.

[ShyCarrot]

Hi, I took longer in this question that I should have because I eliminated the correct answer, E, early on. My rational here was that E did not hurt the conclusion, that being sunscreens do not block UV radiation effectively. Even if people who consistently use sunscreen lotions spend more time in the sun, shouldn’t sunscreen still be able to protect them from UV radiation? Otherwise, if spending more time in the sun leads to cancer im spite of sunblock, doesn’t that still prove Moore’s conclusion is correct that sunblocks do not block UV effectively?

Any help is much appreciated!

[Francis O'Rourke]

Hi ShyCarrot!

Moore claims that sunscreens do not effectively block cancer-causing UV radiation. She draws this conclusion on the basis of studies which observed two groups of people: one group of people who consistently use sunscreens and another who rarely or never use sunscreens.

Using a study is a great idea to test the efficacy of sunscreen. There is one key elements of a good study that is missing from her evidence: we do not know if there was anything different about the two groups that may have influenced their likelihood of developing skin cancer.

Answer choice (E) points out that oversight. If one group of people is much more likely to develop skin cancer, but does not, then something must have inhibited their rates of skin cancer. This is good evidence that the sunscreen they used did effectively lower their incidence of skin cancer.

You pointed out that people who spend time in the sun and use sunscreen still get skin cancer. That is true, but it is not the issue. Moore's use of the phrase "designed to block skin-cancer-causing ultraviolet radiation," does not mean that sunscreen must block all causes of skin cancer.

Sunscreen does not have to completely eliminate skin cancer to show that it is effective. We merely have to show that it effectively blocks one source of skin cancer. If someone who works outside in the sun for 10 hours per day and uses sunscreen is at as much risk as someone who works in a cubicle, I would call sunscreen 'effective.'

Take the following example. Say that after studying people who wear hardhats at work everyday, we find out that these people experience brain injuries at exactly the same rate as people who do not wear protective head gear to work. Can we conclude anything about the efficacy of hardhats? Well, I would expect that people who wear hardhats to work at at an increased risk of brain injuries, so knowing that they have the same rate of head injuries as people who work in an office would be good evidence that hardhats effectively lower risk of brain injury. Construction workers may be at some risk for brain injuries—for example in car accidents or playing sports on the weekend—but that does not make me question whether hardhats work effectively.

I hope this helps, but let me know if you have any other questions!

[ShyCarrot]

Thank you, that was really helpful! That analogy also really cleared up everything for me!

[dbrowning]

Hi,

My prephrase for this question actually matched both B and E fairly well, as there are many more questions nearly identical to this. My prephrase was something to the extent of: 'What if the people who consistently use sunscreen would have been worse off had they not used sunscreen?' With this prephrase, I could not shake AC B and ended up choosing B after skipping and returning to this question at the end. My thought was that severity of the cancer has to be in some way relevant to the effectiveness of sunscreeen. In the explanation, B is rejected on the following grounds: "The occurrence of skin cancer at all, if caused by exposure to ultraviolet radiation, would indicate that the radiation was not blocked by the sunscreen lotion.". Yet, this same reasoning applies to E. Regardless of whether they spend more time in the sun, if people who consistently apply sunscreen still get cancer after more time in the sun, it implies the sunscreen is ineffective. Given this, I do not understand the distinction between B and E, unless E is better simply because we do not know, with respect to B, which group had more severe cases of cancer?

Should my prephrase have been tighter, or did I just read into an easy question too much? Thanks

[James Finch]

Hi D.,

The key here is to know the scope of the conclusion precisely, which is that sunscreen does not block cancer-causing UV radiation effectively. So the issue here is whether people get cancer or not, not how severe the cancer is; the stimulus is arguing that if sunscreen were effective, people wouldn't get cancer period. The big problem here is that we don't know enough about the two groups mentioned, the one that wears sunscreen and the one that doesn't. Are they actually alike, or are there other confounding factors, like climate and amount of sun exposure? The stimulus assumes they're alike in terms of possibility of developing cancer, and this assumption is the flaw we want to Prephrase. (E) is the only answer choice that addresses this, which is why it is correct, while (B) focuses on a related but distinct issue to what the stimulus is concerned with.

Hope that clears things up!

[lsatstudy2023]

Is there a chance that B weakens the stimulus?

[Luke Haqq]

Hi lsatstudy2023!

Answer choice (B) wouldn't weaken the argument.

A problem with the stimulus is that it's possible that there are salient differences between the groups under consideration in the stimulus (those why consistently apply sunscreen, and those who do not). Answer choice (E) captures this--it indicates that the former group might be out in the sun more than the latter group. As the administrator's explanation notes, in this way the stimulus fails to account for a possible alternative cause as to why the former group develops skin cancers as often as the latter group.

Answer choice (B) doesn't address possible differences between the groups. In addition, if you understand why (E) is correct, that alone should be sufficient evidence that (B) wouldn't weaken the argument. That's because weakening it would be a form of identifying a flaw in the stimulus. Since only one answer choice will correctly identify a flaw with the argument, knowing (E) is correct tells you that the other answer choices will not weaken the argument.