PrepTest 136, Section 4, Question 25
Numerous studies have demonstrated a pronounced negative correlation(93 more words not shown)
The argument's reasoning is vulnerable(9 more words not shown)
- Athe consumption of(7 more words not shown)
- Bthe risk of(9 more words not shown)
- Cfiber is difficult(8 more words not shown)
- Dthe fiber in(14 more words not shown)
- Efoods containing fiber(12 more words not shown)
Reading the argument
The pattern is clear. The cause is not.
People eating more fiber-rich foods tend to have lower rates of colon cancer. The comparisons across countries and within Scandinavia reinforce that association. But what else goes along with those diets? Perhaps access to medicine or some other feature of the populations helps explain the difference.
The conclusion singles out fiber itself: too little causes colon cancer, and enough prevents it. That could be true, but the evidence has not isolated fiber from the other differences between the groups or foods. Repeating the association in another setting does not automatically eliminate those alternatives.
What we’re looking for
The flaw question asks for an overlooked possibility. I'd look for another factor that could account for the lower cancer rates while leaving the observed dietary pattern intact.
Working the answers
- A
Increasing fiber consumption over time does not identify an alternative cause of the cancer pattern. We would also need information about how cancer rates or other relevant factors changed. The trend alone neither establishes nor challenges fiber's causal role.
- B
A reduction in other kinds of cancer would not explain away the observed association with colon cancer. This answer presents another possible benefit of high-fiber diets rather than a competing explanation for the evidence at issue.
- C
Difficulty obtaining or eating enough fiber concerns how practical the diet is. It does not show what consuming fiber does biologically. Something could be hard to include in a diet and still prevent disease when consumed.
- D
Different degrees of cancer-fighting benefit would still give fiber a beneficial role. The conclusion does not require cereal fiber and fruit or vegetable fiber to be equally effective. Variation between sources does not expose the failure to separate fiber from other possible protective factors.
- ECorrect
The foods contain other substances that help prevent colon cancer. People who eat those foods consume both the fiber and those other substances, so the cancer rate could track the food without fiber itself being the protective ingredient. The studies as described have not separated those possibilities. E does not prove fiber has no effect; it shows why the observed correlation alone cannot establish the particular causal claims made.
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