Logical ReasoningDifficulty: Easy

PT136 S4 Q25 Explanation

Numerous studies have demonstrated

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

TopicsFlaw

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Full official LSAT questions are available through LawHub. This page provides LSAT Lab's explanation, strategy, and review tools without republishing the full official question.

Stimulus

Numerous studies have demonstrated a pronounced negative correlation between high-fiber diets and the incidence of colon cancer. For example, the colon cancer rate in Western countries is much higher than in many non-Western countries where people eat more fiber-rich foods, such as fruits and vegetables. Furthermore, in Scandinavia it has been conclusively shows that insufficient consumption of fiber causes colon cancer, and sufficient consumption of fiber prevents it.

What this question is testing

Flaw

Your task

Describe the reasoning error the argument actually commits.

Common trap

Answers that name a real logical flaw the argument doesn't actually make.

Winning move

Articulate the gap in the reasoning yourself, then match it to the choice that describes that gap.

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

The question
25.

The argument's reasoning is vulnerable to criticism because the argument overlooks the

Answer choices

  1. No Impact1% picked this

    the consumption of fiber in many countries is

    This doesn't help us assess whether or not fiber is having a causal effect on colon cancer. If we were told "the consumption of fiber is rising appreciably but the rate of colon cancer is steady / falling" then that could Weaken.

  2. Out of Scope: other cancers Strengthens2% picked this

    the risk of many types of cancer is reduced by

    This mildly strengthens by boosting the plausibility somewhat that high-fiber might help prevent against colon cancer (since it reduces the risks of other cancers).

  3. Out of Scope: difficulty3% picked this

    fiber is difficult for many people to include in

    We're trying to assess whether or not fiber has a causal influence on colon cancer. The difficulty of including fiber is irrelevant. You can agree that "running up and down 500 steps will strengthen your legs and heart", even if running up and down 500 steps would be difficult to do.

  4. No Impact13% picked this

    the fiber in fruits and vegetables and the fiber in cereals have cancer-fighting properties

    Without knowing what "different degrees" means, this answer doesn't really tell us anything. This could only really weaken if we found out that, "yes, cereal has fiber, but it's not the type of fiber that fights cancer", making the author's Scandinavian premise seem less relevant.

  5. Correct81% picked this

    foods containing fiber also contain other substances that, when consumed, tend to

    Why this is right

    This gives us the classic 3rd factor way of providing a different explanation for a correlation. Maybe foods with lots of fiber have lots of iron, and iron helps prevent colon cancer. That would explain why eating lots of fiber is correlated with lower rates of colon cancer, but it would be wrong to say that "fiber decreases your risk" if it's really just the iron in the fibrous foods. It would allow the author to conclude "eating fibrous foods reduces your risk of cancer".

    Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.

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