Logical Reasoning

PT12 · S4 · Q20 A new gardening rake with an S-shaped handle

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A new gardening rake with an S-shaped handle reduces compression stress on the spine during the pull stroke to about one-fifth of what it is with a straight-handled rake.

Conclusion

Straight-handled rakes are better than the new S-shaped rakes for minimizing risk of spinal injury.

Evidence

The new rake reduces compression stress on the pull stroke (1/5 of the straight rake) but multiplies it on the push stroke (5x the straight rake, above the danger level). Neither stroke with a straight-handled rake produces enough compression stress to cause injury.

Evaluate

The argument compares the two rakes only on compression stress. But "spinal injury" could come from many sources besides compression stress. If pulling causes injury through some other mechanism, the new rake (which dramatically reduces compression stress on the pull) might still be safer overall. The argument needs the assumption that compression stress from pushing is the only injury cause from raking.

Goal

Find an answer that, if true, lets the conclusion follow — most likely an answer that says compression stress on the push is the only relevant injury source.

20.

The conclusion above is properly drawn from the premises given if which one of the following is true?

  1. Correct

    Compression stress resulting from pushing

    Why this is right

    This is the assumption that makes the argument work. If compression stress from pushing is the only cause of raking-related spinal injuries, then the new rake (which puts pushing stress above the danger level) is the only one that causes injury, while the straight rake (which never reaches the danger level) does not. The conclusion that the straight rake is safer follows directly. Without this assumption, other injury sources could matter and the new rake might come out ahead.

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

    73% picked this

  2. Raking is a frequent cause

    Out of Scope

    How frequent raking-related spinal injuries are among gardeners does not affect which rake is safer. Even if injuries are rare, one rake can still be safer than the other. The conclusion is comparative, and frequency does not bridge the comparison.

    6% picked this

  3. The redesign of a tool

    Out of Scope

    This is a sweeping claim about tool redesigns in general. The argument is about a specific spinal-injury comparison. Whether or not redesigns usually involve trade-offs does not give us the missing link between the compression stress data and the safety conclusion. The argument needs an assumption about what causes injury, not about redesigns in general.

    8% picked this

  4. A garden rake can never

    No Impact

    This says you cannot use a rake using only push strokes. That is true (you have to pull at some point), but it does not close the gap. The argument's issue is whether pushing is the only injury source — not whether pushing is the only stroke type. Even if both strokes happen, we still need to know whether pull-stroke factors (or non-compression factors) matter for injury.

    9% picked this

  5. It is not possible to

    Out of Scope

    The argument is comparing two specific rakes, not surveying every possible handle design. Whether other designs could exist is irrelevant to whether the straight rake is safer than the new S-shaped rake. This does not close the injury-source gap.

    4% picked this

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