LR Question 24 Explanation
QUESTION TEXT: Medical researcher: As expected, records covering the…
QUESTION TYPE: Weaken
CONCLUSION: Adequate prenatal care significantly decreases the risk of low birth weight babies.
REASONING: Hospital records indicate that babies born prematurely are more likely to have low birth weights. The same records note that mothers who received prenatal care were less likely to give birth to an underweight baby.
ANALYSIS: This is a causation-correlation error. There could be some other cause. Perhaps healthy, conscientious mothers (who are likely to have healthy babies) have prenatal care because they think they are supposed to.
That would mean it is the traits of the mothers that leads to healthy babies, not pre-natal care.
That’s just one alternative explanation. The right answer instead shows that doctors aren’t keeping good records.
___________
- This was to be expected. The doctor didn’t say prenatal care would eliminate low birth weights. He just said it would decrease their likelihood.
- CORRECT. This shows that doctors have biased the hospital records. When a baby is underweight they simply assume that there was no prenatal care.
- This doesn’t tell us about pre-natal care.
- As with answer choice A this is to be expected. The doctor said prenatal care produced better results but he didn’t claim it produced perfect results.
- This strengthens the argument. We want to weaken it.
More Resources for Weaken Questions
- Intro Course lesson: This intro course lesson covers Weaken questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers weaken questions.
Hi! Looking for some help here.
Premise 1: if baby is born prematurely, it will have low birth weight and suffer from health problems.
Premise 2: If mother doesn’t receive adequate prenatal care, less likely to have low birth weight baby
Conclusion: Prenatal care significantly decreases the risk of low birth weight babies.
To me, (C) undermines premise 1. Is the problem that premise 1 is just irrelevant to the conclusion? I see how (B) is better, because it undermines premise 2 and premise 2 is more relevant to the conclusion. But did they really throw out a premise that’s just totally irrelevant?
Just a quick correction to premise 2 (I’m assuming you just miswrote, but for clarity’s sake): Receiving adequate prenatal care = less likely to have low birth weight baby.
It’s not that premise 1 is irrelevant, but you’re correctly noticing that it’s not the causal support the conclusion relies on. The conclusion is drawn from the correlation in premise 2, and it assumes that correlation reflects a real effect of prenatal care rather than some issue with the data.
C says low birth weight babies were routinely classified as premature. This suggests that the prematurity <-> low birth wight relationship may be partly circular or inflated, which undermines premise 1. But even if that was the case, premise 2 still remains: adequate prenatal care correlates with fewer low birth weight babies. And that’s the evidence actually relied upon for the conclusion. So C attacks more of a background fact than the gap in the reasoning, whereas B directly undermines this gap.
And just as a general note, not everything in the stimulus will always be relevant to the argument. Some things will be fluff (background context). I wouldn’t quite call premise 1 entirely fluff here, but you’re right that it’s not carrying the weight of the reasoning in the argument. The relationship the argument focuses on is between prenatal care and birth weight, and C doesn’t address prenatal care at all.
Hope that helps! Let me know if you have further questions.