Logical Reasoning

PT144 · S4 · Q7 Dietitian: Eating fish can lower

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Dietitian: Eating fish can lower one's cholesterol level.

Conclusion

Eating fish can lower one's cholesterol level.

Evidence

(1) Two groups were studied. (2) The first group ate a balanced diet including two servings of fish per week; the second ate a similar diet without fish. (3) The first group showed lower cholesterol levels, on average, than the second group. (4) The two groups had displayed similar average cholesterol levels prior to the study.

Evaluate

The argument relies on a study that compares two groups. To support the conclusion that fish caused the lower cholesterol, the study must rule out the obvious alternative: that the fish group already had lower cholesterol going in. The "similar pre-study cholesterol" claim does exactly that — it eliminates the pre-existing-difference explanation, leaving the dietary difference as the operative variable.

Goal

Find an answer that captures this role: the claim rules out an alternative explanation for why the fish group ended up with lower cholesterol.

Which one of the following most accurately describes the role played in the dietitian's argument by the claim that the two groups had displayed similar average cholesterol levels prior to the study?

It is offered as an
Wrong Role
The claim isn't an objection — it's the dietitian's own evidence supporting the conclusion. The dietitian is using the similar-starting-cholesterol fact to strengthen the inference that fish caused the difference. An "objection to the main conclusion" would push against the conclusion; this claim pushes for it.
0% picked this
It expresses the main conclusion
Wrong Role
The main conclusion is "Eating fish can lower one's cholesterol level." The claim about pre-study cholesterol levels is supporting evidence, not the main conclusion itself. The conclusion makes a claim about what fish does to cholesterol; the referenced sentence makes a claim about the study setup.
1% picked this
Correct
It rules out an alternative
Why this is right
This captures the role precisely. Without the pre-study claim, an obvious alternative explanation hangs over the result: maybe the fish group already had lower cholesterol going in, with no role for fish at all. By stating that both groups started at similar cholesterol levels, the dietitian rules out that alternative — leaving the dietary difference (fish vs. no fish) as the variable that produced the result.
Skill tested: Role · how this choice captures the argument's function is the move to repeat next time.
92% picked this
It provides background information on
Wrong Role
The claim isn't background — it's active, load-bearing evidence. Background information typically gives context without affecting the strength of the argument. This claim directly affects the strength of the inference: removing it would let the alternative explanation (pre-existing difference) survive, undermining the conclusion.
6% picked this
It introduces an alternative explanation
Wrong Role
The claim doesn't introduce an alternative explanation; it rules out an alternative explanation (that the fish group had lower cholesterol from the start). This answer reverses the direction of the claim's function.
1% picked this

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