PrepTest 153, Section 3, Question 17
After monitoring blood levels of lycopene (a nutrient(49 more words not shown)
Which one of the following,(6 more words not shown)
- AMost fruits and(24 more words not shown)
- BCountries in which(18 more words not shown)
- CMiddle-aged people typically(7 more words not shown)
- DStudy participants with(21 more words not shown)
- EThere was wide(7 more words not shown)
Reading the argument
Why single out lycopene?
It comes from some fruits and vegetables, so perhaps the people with more lycopene also eat differently in other ways. Picture two people's meals: one regularly includes a range of fruits and vegetables, while the other rarely does. Those diets could differ in many nutrients, not just the one the researchers measured.
That is an imagined difference, not something the study has established about every participant. Low lycopene doesn't mean no lycopene, and it certainly doesn't tell us that someone eats no fruits or vegetables. But it gives us a possible alternative to investigate: maybe the broader diet helps, and the measured nutrient is getting the credit.
What we’re looking for
We can accept the reported stroke rates and still question that credit. For the weakener, I'd look for a reason another part of the diet could be responsible. Showing a specific alternative would make the researchers' 'clearly' much harder to defend.
Working the answers
- ACorrect
These foods contain other nutrients thought likely to reduce stroke risk. Now we have more than a vague suspicion that the diets might differ. We have a particular kind of difference that could affect the very outcome being measured.
A person eating the lycopene-rich food could receive lycopene and those other nutrients together. If the other nutrients supplied the protection, we could still observe high lycopene alongside fewer strokes. So the observed relationship doesn't isolate lycopene's effect. A weakens the argument without having to prove that lycopene contributes nothing.
- B
The same broad pattern also appears between countries: more lycopene-rich foods goes with fewer strokes. That could be additional evidence for the researchers' theory, although it still leaves the other contents of those foods entangled with lycopene. It doesn't supply a reason to prefer a competing explanation.
- C
All the study participants were middle-aged. A comparison with young adults doesn't explain why the middle-aged participants with lower lycopene had more strokes than the middle-aged participants with higher levels. It changes the groups we are comparing.
- D
This deserves attention because it confirms a dietary difference: one group ate twice as much fruit and vegetables on average. That could lead us toward our alternative. It isn't redundant; blood levels alone never told us how much of those foods each group consumed.
But A goes further. It identifies other nutrients in the same foods that are thought likely to reduce stroke risk. D gives a quantity difference; A gives a competing protective factor. That is the more direct challenge to crediting lycopene itself.
- E
A wide range of lycopene levels lets the researchers compare people at different levels, but it doesn't explain the different stroke rates. It gives no other cause to investigate and no reason the observed association should be interpreted differently.
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