Logical Reasoning

PT149 · S1 · Q5 Researchers examined 100 people

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Researchers examined 100 people suffering from herniated disks in their backs.

Conclusion (they concluded)

The genetic defect increases the likelihood of herniated disks.

Evidence

5 of 100 people who had disk problems had a defect in gene X. 0 of 100 people who didn't have disk problems had a defect in gene X.

Evaluate

This argument is a little weird, because 95 of the 100 people who had disk problems did not have any issues with gene X. But the author's thought is that,

The author isn't arguing that everyone with back problems has a messed up gene X, just that it increases the likelihood of herniated disks.

Goal

We can strengthen this by ruling out an alternate explanation for why the 5 (of 200) people who had messed up gene X were all people with herniated disks (i.e. rule out the idea that having a herniated disk can cause gene X to be messed up / rule out the idea that some 3rd factor is causing both a deformed gene X and a herniated back).

We can also strengthen this by making it seem more plausible that this genetic defect increases likelihood of a herniated disk (more data points where the defect and the herniated disks go together).

5.

Which one of the following, if true, most strengthens the researchers' reasoning?

  1. The researchers also examined a

    Weakens, if Anything

    This answer is offering what seems to be Effect w/o Cause, because it's talking about data points that have the supposed effect (herniated disk) but don't have the supposed cause (genetic defect). But we already had 95 examples in the argument of people who have a herniated disk but don't have a defective gene. So getting 80 more with that profile doesn't change anything.

    0% picked this

  2. When the researchers examined a

    Unclear Impact

    This certainly doesn't seem like impressive evidence for the author's conclusion. If he thinks that this defective gene increases the odds of a herniated disk, then it's not very compelling to say that 2% of people with the gene have herniated disks. But this answer could potentially still strengthen. We would need to know what percent of the general population ends up with herniated disks. If only 1% of the general population gets a herniated disk, but 2% of the population with this defective gene gets a herniated disk, then that would strengthen the idea that this gene increases the likelihood of getting a herniated disk.

    1% picked this

  3. Correct

    When the researchers examined the

    Why this is right

    This adds more data points in which the supposed cause (defective gene) and supposed effect (higher likelihood of herniated disk) go hand in hand. This one is 30 for 30. All 30 of the family members that had the defective gene suffered from herniated disks. That's strong evidence that this defective gene is influencing risk of herniated disks.

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

    98% picked this

  4. Another team of researchers examined

    Weakens

    This is giving us Cause w/o Effect weakening data points. These 100 people have the supposed cause (defective gene) but don't have the supposed effect (herniated disk).

    0% picked this

  5. When the researchers examined the

    Weakens, if Anything

    This only provides us with 20 Effect w/o Cause data points, which weaken the argument. These 20 people had the supposed effect (herniated disks) but didn't have the supposed cause (defective gene).

    0% picked this

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