Logical ReasoningDifficulty: Medium

PT6 S3 Q7 Explanation

Head injury is the most serious

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

TopicsNecessary Assumption

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Stimulus

Head injury is the most serious type of injury sustained in motorcycle accidents. The average cost to taxpayers for medical care for nonhelmeted motorcycle-accident victims is twice that for their helmeted counterparts. Jurisdictions that have enacted motorcycle-helmet laws have reduced the incidence and severity of accident-related head injuries, thereby reducing the cost horseback-riding accidents are even more likely to cause serious head injury than motorcycle accidents are.

What this question is testing

Necessary Assumption

Your task

Find the assumption the argument requires in order for its conclusion to hold.

Common trap

Answers that would help the argument but aren't strictly required (sufficient, not necessary).

Winning move

Negate each choice — the right one breaks the argument when negated.

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 is an assumption upon which the author’s conclusion concerning helmets for

Answer choices

  1. Correct73% picked this

    Medical care for victims of horseback-riding accidents is a financial drain

    Why this is right

    One of the similarities the author is assuming is that there is money to be saved on horseback riding injuries. If those injuries are currently paid by rich people's private healthcare, then whether a horseback rider wears a helmet or not doesn't really affect the city. If medical care for horseback-riding injuries isn't a financial drain on taxpayers, then there'd be no taxpayer cost-saving benefit in passing helmet laws. And that weakens the author's argument, since she said we should enact these laws for the same reason (reducing cost to taxpayers).

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

  2. Irrelevant Causality1% picked this

    The higher rate of serious head injury suffered by victims of horseback-riding accidents is due to the difference in

    This is speculating the causal backstory to a premise. We know that horseback-riding accidents have a higher rate of serious head injury. It doesn't matter to the author's argument whether that's because of the difference in size between horses/motorcycles, or difference in size between horseback riders and motorcycle riders, or the type of terrain they each tend to be on, or any other reason. The logic is simply, "We saved money on motorcycle head injuries by requiring helmets. Horseback riding head injuries are even more common. So let's require helmets there too and save some money."

  3. Irrelevant Comparison7% picked this

    The medical costs associated with treating head injuries are higher than those for other

    This has the classic "out of scope comparison" wording, other than [what we were talking about]. This argument was about head injuries and was never comparing them to other types of injuries. Trap answers love to act like "the only thing we talked about" is the only thing that has the traits we discussed / or the most important thing / or the most prevalent thing.

  4. Too Strong15% picked this

    Most fatalities resulting from horseback-riding and motorcycle accidents could have been prevented if the victims

    Too Strong: most Out of Scope: fatalities (D) is about fatalities, not medical costs or financial implications. The argument is about cost reduction, not death prevention. And the word "most" is famously wrong on Necessary Assumption, 98% of the time. It rarely makes a crucial difference to an argument whether something would be true in 49% of cases vs. in 51% of cases.

  5. Opposite (if anything)4% picked this

    When deciding whether to enact helmet laws for motorcyclists and horseback riders, the jurisdiction’s primary concern is the

    The only concern mentioned in the argument that motivates the decision to enact these laws is cost reduction to taxpayers.

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