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 (therefore)

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

We're trying to prove that one rake is better than the other when it comes to risk of spinal injury.

Does the premise provide some sort of rule for "risk of spinal injury"? How do we assess which one has higher risk?

We say that the straight rake doesn't produce enough compression stress with either stroke to cause injury, whereas the S-rake's push stroke causes enough compression stress to be dangerous.

So when it comes to compression stress, we already know that the straight rake beats the S-rake. Does that mean, we already know that the straight rake beats the S-rake overall when it comes to risk of spinal injury?

We can't already know that, or else there wouldn't be a correct answer choice. How could straight rakes still lose the battle of spinal risk?

Goal

The only way straight rakes would lose the risk comparison is if there were something else about using a rake that could cause spinal injury.

If compression stress were the only thing to worry about, then straight rakes have already won.

So let's look for an answer ruling out all other possible ways rakes could cause spinal injury, or, equivalently, locking in compression stress as the only thing we need to worry about.

20.

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

Correct
Compression stress resulting from pushing
Why this is right
Yeahhhh, boi! If the only spinal risk comes from compression stress, then we know that straight rakes win. Neither stroke produces enough CS to cause injury, whereas the push stroke of an S-rake is above the danger level. Sometimes when we read an argument on Suff Assump, we feel like "they've already proven the conclusion?" We know that can't be right, but the argument's logic feels internally solid. That usually means that the conclusion is making a broader claim than what the evidence actually proved. The valid conclusion from the evidence would be, "straight rakes are better than new rakes for minimizing risk of spinal injury from compression stress." We want an answer to make it seem like, "What we talked about in the evidence is all we need to talk about, to judge the conclusion." We have a tag for this style of argument called "Make the Evidence Universal", which is meant to convey the idea of, "if you tell me that the discussion of compression stress is all I need to care about, then yes you've proven your conclusion."
Skill tested: Sufficient Assumption · how this choice captures the argument's function is the move to repeat next time.
72% picked this
Raking is a frequent cause
Out of Scope
This has nothing to do with our goal of ruling out other possible rake-related sources of spinal injury. 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.
7% picked this
The redesign of a tool
Out of Scope
We don't want to see new ideas creep in, on Sufficient Assumption answers, so it's a big red flag to suddenly be talking about "efficiency". We also want super strong / no-exceptions type answers, so the squishiness of "rarely" is also a turn-off. This has nothing to do with proving that compression stress is the only risk of spinal injury we need to worry about.
7% picked this
A garden rake can never
No Impact
This says "you're always going to have some pull strokes". That's actually moving in the opposite direction of the argument. The author is arguing that straight rakes are lower risk for spinal injury on the basis that straight rakes are safer when it comes to push strokes. Straight rakes are tied with S-rakes when it comes to pull strokes, so an answer that emphasizes that "there will be pull strokes" isn't helping us prove that straight rakes are safer.
9% picked this
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.
5% picked this

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