Researchers announced recently that over the past 25 years the incidence of skin cancer caused by exposure to harmful...

Cynthia-Lee on September 12, 2018

Please explain

I don't get how B weaken the argument that using sun screen is unlikely reduce a person's risk of developing skin cancer. Please help me understand this question,thanks

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Shiyi-Zhang on February 26, 2019

Why is E incorrect?

Ravi on February 28, 2019

@Cynthia-Lee and @Shyi-Zhang,

Happy to help!

In the stimulus, we're told that over the last 25 years, sunscreen use
has risen, but skin cancer rates have also gone up. From this, the
argument concludes that sunscreen likely doesn't reduce skin cancer

In examining this argument, it seems decent upon first glance. If
sunscreen use has risen over the last 25 years, then if it helped
prevent or reduce skin cancer risk, we'd think that we would have seen
a decrease in skin cancer rates over the same time (but the opposite
has happened).

The question is asking us to pick an answer that would weaken the
argument. In other words, we're looking for an answer choice that
suggests that sunscreen does help to reduce skin cancer rates. What if
there were an alternative cause of the rising skin rates, or what if
sunscreen use were concentrated in certain regions where skin cancer
was actually going down (but overall, skin cancer nationwide or
globally was still going up)?

(E) says, "Those who use sunscreens most regularly are people who
believe themselves to be most susceptible to skin cancer."

(E) is basically saying that the people who use sunscreen are the ones
who think they have a higher skin cancer risk. The problem with (E) is
just because these people think they are most susceptible to skin
cancer doesn't necessarily mean that they are. Additionally, even if
we assume that they're correct in that they're more likely to develop
skin cancer since they're using sunscreen most regularly we would
suspect that if the sunscreen actually worked, we would be seeing
their rates go down. Remember, we're trying to weaken the argument,
and (E) isn't providing us with anything to help us accomplish our
goal of weakening. We can get rid of this answer choice.

(B) says, "Skin cancer generally develops among the very old as a
result of sunburns experienced when very young."

(B) provides us with information that would help to seriously weaken
the argument because if people develop skin cancer when they're really
old, then it's reasonable that the increase in sunscreen use over the
last 25 years wasn't over enough time to meaningfully affect skin
cancer rates among the elderly, where skin cancer often shows up. It's
possible that these people already had their bad exposure to the sun
before the last 25 years. It's even possible that they started using
sunscreen a lot over the last 25 years but had already had too much
sun exposure and set themselves up for skin cancer later on. This
answer choice suggests that it's still possible that sunscreen use
could be effective in reducing skin cancer risk, so this helps to
weaken the argument. (B) is the correct answer.

Does this make sense? Let us know if you have any more questions!