Logical Reasoning

PT16 · S3 · Q24 A birth is more likely to be

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A birth is more likely to be difficult when the mother is over the age of 40 than when she is younger.

Conclusion

There must be more ambidextrous people born to women over 40 than ambidextrous people born to women 40 and under.

Evidence

When you're over 40, a birth is more likely to be difficult than it is when you're 40 or less.

A person whose birth is difficult is more likely to be ambidextrous than one whose birth wasn't difficult.

Other causes of ambidexterity are not related to mother's age.

Evaluate

The conclusion should seem a little counterintuitive to us. After all, not a ton of people are born to women over 40 (especially back in the day of Test 16). You could take any trait in the world, and your default assumption would be that there are more people with that trait who were born to women in their 20s and 30s than to women in their 40s or above.

The reason the author is getting to this counterintuitive conclusion is because if you are having a kid and you're over 40, your chances of a difficult birth are higher and thus your chances of having an ambidextrous kid are higher.

But higher chances doesn't mean higher numbers, because the latter is still impacted by the underlying population size of each group (people who give birth at age 40 or under > people who give birth over 40).

As an analogy, suppose we say

Could we conclude that ? No, of course not. Even though being in that position of climbing a telephone pole makes you more likely to get a splinter, the population size of telephone pole climbers is way, way smaller than the rest of the population, so someone with a splinter is still more likely to not have the job of climbing telephone poles.

Goal

Let's look for an answer saying that, .

Maybe 15% of births from women over 40 result in ambidexterity whereas only 5% of births from women under 40 do so.

But 15% of 100 is still less than 5% of 1000, so if there are way more children born to moms under 40, then there could easily be way more ambidextrous people born to moms under 40.

24.

The argument is most vulnerable to which one of the following criticisms?

  1. It assumes what it sets

    Not Circular

    This answer describes one of the top 10 Famous Flaws, Circular Reasoning, in which the evidence restates the conclusion or assumes the truth of the conclusion. This answer is almost never correct. This argument did not restate its conclusion as a premise. And none of the premises logically necessitate the conclusion.

    18% picked this

  2. Correct

    It overlooks the possibility that

    Why this is right

    This is what we were predicting. We can object to this author that, "Yes, a women over 40 is more likely to have an ambidextrous child, but women over 40 are only responsible for 10% of babies born, so even though women under 40 are less likely to have an ambidextrous child, they have so many more babies than do women over 40 that these younger women are still going to produce a higher total number of ambidextrous babies." We could call this argument an example of the classic % vs. #'s flaw, in which an author assumes that a higher percent therefore represents a higher raw number.

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

    66% picked this

  3. It fails to specify what

    Never a Correct Answer

    This type of answer shows up a lot on Flaw but is never correct. It asks for specific names, specific measurements, specific amounts, specific definitions. We're here to judge reasoning flaws, not scrutinize the exact details. Would it make any difference to this argument whether 17% of the population as a whole is ambidextrous vs. 19% of the population? Of course not. Neither specific percentage would change this reasoning at all.

    4% picked this

  4. It does not state how

    Not Necessary

    When an answer says that the author fails to establish X does not specify / state X we're implying that the author should have done so. Their argument needed them to specify X. Does this author need to tell us the precise age at which point we ascertain whether you're leftie, rightie, or ambidextrous? No, it wouldn't make any difference to the conversation whether you have to be 3 years old vs. 5 years old before we can make that determination.

    0% picked this

  5. It neglects to explain how

    Not Necessary

    When an answer says that the author fails to establish X does not specify X neglects to explain X we're implying that the author should have done so. Their argument needed them to specify / establish / explain X. Does this author need to tell us how a turbulent trip down the birth canal results in ambidexterity? No, it wouldn't in any way affect how we assess the very quantitative conclusion. We're accepting the premise that difficult births are more likely to end up with an ambidextrous baby, and we're scrutinizing whether accepting that fact will force us to believe that more ambidextrous babies came from older moms.

    12% picked this

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