LSAT 16 - Section 3 - Question 24

Here we have a flaw question, which we know from the question stem: A flaw in the reasoning of the passage is that it…” Right away we know our correct answer has to do two things: be descriptively accurate, and describe the flaw of the stimulus. We also know what the wrong answers will do - describe reasoning flaws we’ve seen before, but don’t like up with our stimulus. Once we have a clear understanding of the questrion’s objective, we can proceed into structural analysis of the stimulus.

Our stimulus begins by laying out factual information about the difficulty of giving birth over 40, and the likelihood of a difficult birth leading the child to be ambidextrous. The author claims the facts above prove there must be more ambidextrous babies born to mothers over 40 than there are born to younger mothers.

In order for a comparison conclusion to hold up we need to be able to assume our groups are, well, comparable. This is where we can identify the assumption being made in the argument. Our stimulus supports its conclusion by comparing two groups (younger and older mothers) that are clearly different in one clear regard. A woman is more likely to give birth below the age of 40 than they are above the age of 40.

Let’s consider this to the extreme to best see the problem in this stimulus. Say that we have 10 mothers who gave birth under 40 and only 1 mother who gave birth after 40. This scenario would not allow us to draw the conclusion we see in the stimulus. Sure, the older mother is more likely to have an ambidextrous baby and that mother is more likely to have a difficult birth, but there is no guarantee there will be more ambidextrous babies born to mothers over 40. For all we know, very few women give birth above the age of 40 based on the strictions of our stimulus.

Knowing our flaw that we can’t definitively prove more babies are born to mothers in this age range, we can jump into answer choice elimination.

Answer Choice (A) We know this answer is not descriptively accurate because it accuses our argument of circular reasoning - when we can conclude A happened because A happened. But we do not see an instance of our conclusion being used as evidence for our main point.

Correct Answer Choice (B) This is exactly what we are looking for! This descriptively correct answer choice hits on the problem that the increased likelihood of something occurring does not equal a higher number of that thing will result.

Answer Choice (C) This answer is descriptively accurate, but not the ultimate problem in our stimulus. The percentage of people who are ambidextrous in the entire population does ont weigh on our conclusion comparing specifically those born to older or younger mothers.

Answer Choice (D) This answer is descriptively accurate, but not the ultimate problem in our stimulus. The age of a child in determining handedness is not an issue - if anything, what matters in our discussion is the age of the mother.

Answer Choice (E) This answer choice is descriptively accurate but not our overall flaw. We care about the number of children with this trait rather than the means through which they acquire it. For this reason, we can eliminate answer choice E.