Logical ReasoningDifficulty: Hard

PT152 S1 Q19 ExplanationResearcher: In an experiment, 500 families

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

TopicsFlaw

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Stimulus

Researcher: In an experiment, 500 families were given a medical self-help book, and 500 similar families were not. Over the next year, the average number of visits to doctors dropped by 20 percent for the families who had been given the book but remained unchanged for the other families. Since improved family having a medical self-help book in the home improves family health.

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
19.

The reasoning in the researcher’s argument is questionable

Answer choices, explained

  1. Not Our Biggest Gripe9% picked this

    it is possible that the families in the experiment who were not given a medical self-help book acquired medical

    Yes, the author's causal story does indeed assume a difference between the book-group and the non-book group. If the non-book group also had medical self-help books, then the author would need some other way to explain the 20% difference. Ultimately, this answer is just less direct of a criticism than the correct answer is. The illegal backwards move and the failure to consider alternate explanations for why the book-group had 20% fewer visits are the two big reasoning flaws. This objection is kind of just nitpicking at a premise, making it seem like there wasn't a difference between the two groups in the first place. That doesn't provide a different way to explain the 20% difference (if both groups had self-help books, then we have no idea why one group is visiting docs 20% less than the other). If we had an argument that said, "Jumping off a tall building will lead to a broken bone. Jim has a broken bone. Thus he must have jumped off a tall building", our primary objections would be the backwards logic or the failure to consider alternate explanations, not "it is possible that a tall building has a lot of bushes at ground level to cushion one's fall".

  2. No Impact12% picked this

    the families in the experiment could have gained access to medical self-help information

    This is similar to (A), but it doesn't do a great job telling us which families we're even talking about. In order for this to weaken, we'd need to know that the families in the book-group got medical self-help info from some other source, and that info is why they saw the doc 20% less. That would undermine the argument that medical self-help books improve family health by making it seem like the medical self-help book didn't have anything to do with the improved family health. This answer doesn't discriminate between the two groups, so it doesn't give us an alternative way to explain the data. And the author didn't need to assume that people's only access to medical self-help info is books.

  3. No Impact15% picked this

    a state of affairs could causally contribute to two or more

    In order for saying, "Hey, author, X could contribute to Y and Z" to be an objection, our author would have needed to be thinking that a certain causal factor only caused one thing. Our author does think that having a self-help book caused improved family health, and that improved family health caused 20% fewer trips to the doctor. So our author actually already accepts that a state of affair (having a self-help book) could causally contribute (directly or indirectly) to two or more effects.

  4. Correct49% picked this

    two different states of affairs could each causally contribute to the same effect even though neither causally

    Why this is right

    Welcome to the Hall of Nightmares, kids! This correct answer definitely goes in my top 20 worst all time. The way LSAT wanted us to match this up was like this: two diff states of affairs each causally contribute to the same effect improved family health --> fewer doctor visits medical self-help book --> fewer doctor visits even though neither causally contributes to the other the medical self-help book did not causally contribute to improved family health. (nor vice versa, but no one cares about that causal possibility) This answer is getting at the objection we posed that maybe the medical self-help book really did lead to 20% fewer visits, but not because the book improved the families' health; rather, the book just allowed them to self-diagnose and learn how to treat their conditions when they were sick, obviating the need to go visit the doctor.

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

  5. No Impact15% picked this

    certain states of affairs that lead families to visit the doctor less frequently could also make them more likely to have a

    If this argument hadn't been in the context of an experiment, and instead had just been a correlation like "People who own medical self-help books are less likely than those who don't to visit the doctor", then this answer could have pointed out the reverse causality possibility that FIRST came the healthy underlying factors, THEN came buying the medical self-help book. But for this argument, we know that people are given the book as part of the experiment, so it removes this line of objection.

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