PrepTest 148, Section 3, Question 18
Journalist: Scientists took blood samples from two large,(71 more words not shown)
The journalist's argument is most(10 more words not shown)
- AIt presumes that(6 more words not shown)
- BIt overlooks the(29 more words not shown)
- CIt overlooks the(22 more words not shown)
- DIt overlooks the(23 more words not shown)
- EIt takes for(21 more words not shown)
Reading the argument
What about the people who like vegetables? They might all have this gene too.
We have two groups, but the reported analysis covers only the people who dislike vegetables. It's easy to read that as a comparison: the vegetable haters have XRV2G, so the vegetable lovers must not. The passage never says that. A trait shared by one group doesn't automatically distinguish it from another group.
Imagine checking the vegetable haters and discovering that everyone in that group has two eyes. Would that be strong evidence that having two eyes explains their dislike? We'd immediately want to know about the other group. If the vegetable lovers also all had two eyes, the observation wouldn't identify the difference we're trying to explain. The unfamiliar gene name can hide that same missing comparison.
What we’re looking for
For the flaw, I'd look for the assumption that the vegetable lovers don't also all share XRV2G. Finding the gene in both groups wouldn't prove that genetics plays no role. It would show why this evidence hasn't established the genetic explanation being offered.
Working the answers
- A
The conclusion concerns one preference, and even there it says 'at least in some cases.' It doesn't require every human trait to be genetically determined. Other preferences or behaviors could have entirely different explanations.
- B
Any sample could differ from the whole population in some respect. But what relevant difference makes these particular results unreliable? We're told the groups are large and diverse, and no specific sampling defect is identified. The clearer problem occurs even if the samples are excellent: we haven't been told whether the gene distinguishes the two groups at all.
- C
This describes overlooking other ways an effect could occur even when one factor always produces it. But we haven't established that XRV2G always causes a dislike of vegetables. That's part of what needs support. Nor does the modest conclusion require every case of vegetable dislike to have the same cause. C doesn't identify the missing evidence in this comparison.
- D
Other genes could influence vegetable dislike while XRV2G also plays a role. That possibility is compatible with the conclusion that dislike is sometimes genetically determined. We need to question why the shared gene is evidence for that conclusion, not merely add other genetic influences that would fit it.
- ECorrect
The journalist treats the shared gene as evidence explaining the vegetable haters' preference without checking whether the vegetable lovers all share it too. If both groups have the gene in common, its presence alone doesn't distinguish the people who dislike vegetables from those who enjoy them. That doesn't settle every possible interaction between genes and preferences. It exposes the missing comparison behind this particular inference.
More Flaw questions
Learn the LSAT our way
Our platform drills Flaw questions at your level and adjusts as you improve.