Logical ReasoningDifficulty: Easy

PT144 S4 Q7 Explanation

Dietitian: Eating fish can lower

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsRole

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Stimulus

Dietitian: Eating fish can lower one's cholesterol level. In a study of cholesterol levels and diet, two groups were studied. The first group ate a balanced diet including two servings of fish per week. The second group ate a very similar diet, but ate no fish. The first group showed lower cholesterol groups had displayed similar average cholesterol levels prior to the study.

What this question is testing

Role

Conclusion

The dietitian wants you to believe that eating fish can lower cholesterol.

Evidence

The study showed the fish-eating group ended up with lower average cholesterol than the no-fish group.

Evaluate

For Role questions, ask what work the referenced sentence is doing. Here, why mention that both groups started with similar cholesterol levels?

Without that information, an obvious alternative explanation looms: maybe the fish group already had lower cholesterol before the study even started, and fish had nothing to do with the difference at the end. The "similar pre-study levels" claim closes that escape route. With it in place, the only thing different between the groups is the fish — so any cholesterol-difference at the end must trace back to the fish.

That's the role: not the conclusion, not background, not a stand-alone premise — but a specific kind of premise that rules out a competing explanation for the data.

Goal

Pick the answer that says the claim rules out an alternative explanation.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
7.

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

Answer choices

  1. Wrong Role0% picked this

    It is offered as an objection to the main conclusion of

    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.

  2. Wrong Role1% picked this

    It expresses the main conclusion of

    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.

  3. Correct92% picked this

    It rules out an alternative explanation of the data collected in

    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.

  4. Wrong Role6% picked this

    It provides background information on the purpose of

    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.

  5. Wrong Role1% picked this

    It introduces an alternative explanation of the phenomenon described in the

    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.

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