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Resolve the ParadoxX. The correct answer choice is (D)
The stimulus describes two studies that produced discrepant findings about the health benefits of
consuming beta-carotene. In the 24-year study, the subjects with a high intake of beta-carotene-rich
foods were much less likely to die from cancer or heart disease than were those with a low intake of
such foods. On the other hand, a separate study observed no positive or negative effect on the health
of subjects taking beta-carotene supplements for 12 years.
Before attacking the answers, try to explain the discrepancy in your own words. One way to do it
would be to look for critical differences between the studies. After all, since the stimulus contains
a paradox where two items are different, an answer choice implying that they are similar will not
explain the paradox. The most obvious difference between the studies is that one of them observed
subjects over the course of 24 years, whereas the other was completed in only 12 years. This might
explain why the health benefits of beta-carotene were not apparent in the shorter study. Also, the 24-
year study followed subjects whose diet contained beta-carotene-rich foods, whereas the subjects in
the 12-year study only took supplements. If beta-carotene supplements are not as powerful or wellabsorbed
as foods rich in beta-carotene, this would explain why the subjects in the 12-year study
showed no health benefits.
The stimulus is followed by a ResolveX question, which means that among the five answer choices,
the four incorrect answer choices will provide a resolution to the paradox, and the one correct choice
will not provide a resolution.
Answer choice (A): If the human body processes the beta-carotene present in foods much more
efficiently than it does beta-carotene supplements, the subjects in the 24-year study who consumed
foods rich in beta-carotene would be more likely to benefit from it than the subjects who took
beta-carotene supplements in the other study. Because this answer choice resolves the apparent
discrepancy between the two studies, it is incorrect.
Answer choice (B): If beta-carotene must be taken for longer than 12 years to have any cancerpreventive
effects, this would explain why the subjects in the 12-year study showed no health
benefits. Had they been observed for a longer period of time, the cancer-preventative effects might
have been more easily apparent. Because this answer choice resolves the apparent discrepancy
between the two studies, it is incorrect.
Answer choice (C): If foods rich in beta-carotene also tend to contain other nutrients that assist in
the human body’s absorption of beta-carotene, this would explain why the group who consumed
such foods showed certain health benefits that the other group did not. Because this answer choice
resolves the apparent discrepancy between the two studies, it is incorrect.
Answer choice (D): This is the correct answer choice. If the 12-year study randomized the subjects
into two equal groups, one of which was given a placebo and the other—a beta-carotene supplement,
this would only explain why half of the subjects in that study would have had no positive or negative
effect on their health (they received the placebo). However, it is unclear why the other half showed
no benefit either. Because this answer choice does not explain the apparent discrepancy between the
two studies, it is the correct answer.
Answer choice (E): At first glance, this may seem like an attractive answer, since it is not
immediately apparent how it would resolve the paradox. To understand that, recall that any answer
describing a difference in the way in which the two studies are conducted could potentially explain
the discrepancy in their results. If, in the 24-year study, the percentage of subjects with a high intake
of beta-carotene-rich foods who smoked cigarettes was much smaller than the percentage of subjects
with a low intake of beta-carotene-rich foods who smoked, this means that the smokers were more
likely to consume foods that are low in beta-carotene. Since the higher risk of cancer among the
subjects with a low intake of beta-carotene-rich foods could easily be due to their smoking habits,
this would compromise the validity of the 24-year study and explain the discrepancy in the results
between the two studies.
Remember—for a study or a survey to provide a reliable basis for a given conclusion, it needs to
account for other possible causes that can explain the conclusion. This is usually done by control