LR Question 24 Explanation, by LSATHacks
QUESTION TEXT: Physician: The rise in blood pressure that commonly…
QUESTION TYPE: Sufficient Assumption
CONCLUSION: Some older people can lower their blood pressure by drinking milk.
REASONING: Lack of calcium often causes the rise in blood pressure associated with aging. One glass of milk per day has enough calcium to make up for a deficiency. But the deficiency is often caused by a lack of vitamin D that is needed to absorb calcium.
ANALYSIS: This is a bad argument. It presents a problem: we can’t use calcium without enough vitamin D. But then the solution only mentions adding more calcium, and doesn’t address the vitamin D problem.
The correct answer solves this by showing that milk has enough vitamin D to allow calcium absorption.
___________
- CORRECT. This does it. Milk not only provides enough calcium but also the vitamin D to absorb it.
- This shows that milk merely isn’t harmful. But we’re trying to conclude that it will actually improve blood pressure.
- Same as B. This shows that milk doesn’t do damage. But we need to know if it can help.
- That’s good. But it doesn’t tell us how milk helps.
- Yikes. You’d better get some vitamin D. Unfortunately, this doesn’t tell us if milk has vitamin D.
Free Five Part LSAT Email Course
Hi, I'm Graeme Blake
Founder of LSAThacks; I scored a 177 on the LSAT.
I created the LSAT Mastery Seminars, which are part of the Ultimate LSAT Prep Bundle
If you like the explanations you're reading I'm 100% confident you'll enjoy the courses. Satisfaction guaranteed.
---------
Updates:
For updates, sign up for my email list. I update whenever I have new posts.
I’m having a hard time with this one. If “the calcium in one glass of milk makes up for ANY calcium deficiency,” (as the last sentence says), shouldn’t “any” account for all calcium deficiencies, caused by all factors (including those actually due to a vitamin D deficiency)? I don’t understand why we need answer A to get to the conclusion, I feel like the word “any” in the last sentence of the stimulus gets us there already.
Because of the above logic, I chose answer B, which I see as addressing a real problem in the stimulus: what if milk has adverse effects on blood pressure that outweigh the benefits listed in the stimulus.
Any guidance would be appreciated.
Thank you!
How do you know how much of the stimulus to incorporate into your problem solving? For example, on question 17 from this section we knew to dismiss the last sentence. In this question we needed to incorporate the sentences that referenced Vitamin D deficiency. My approach to this question was to focus specifically on lowering blood pressure and milk providing enough calcium. I initially thought Vitamin D was filler to make other answers more attractive.
I don’t think there’s a clear answer to this or a way to generalize. This question and question 17 are both sufficient assumption questions, so the correct answer needs to guarantee the conclusion. For both sufficient and necessary assumption questions, it’s useful to look for a “gap” between the premises, and the correct answer would fill that gap. In that sense, other parts of the stimulus might not be that useful but I suggest considering all parts of the stimulus.
I missed this question because they specifically say that a calcium deficiency will lead to “rise in blood pressure.” The conclusion says that people can “lower their blood pressure” by drinking milk. Nowhere in the argument (or the correct assumption drawn) does it prove that the milk will LOWER their blood pressure. Maybe it will just stabilize it at the level it’s reached. Can you explain why addressing the fact that milk will allow them to get enough Vit D to absorb calcium, and thus replace their calcium deficiency, will NECESSARILY “lower” their blood pressure?
I think this is one of the situations where you should look at the stimulus from the perspective of common sense and not strictly as an LSAT student. In real life, people with high/”rising” blood pressure don’t really look to stabilize their blood pressure. They want to lower it.
If we look at this question with that in mind, then if we were to diagram this question, the first two sentences would look like this: if rise blood pressure –> calcium deficiency –> ~VitD
We have to connect the above premises to the conclusion that milk helps with lowering blood pressure. Since this is a sufficient assumption question, all we have to do is flip the chain around (if VitD –> ~calcium deficiency –> ~ rise blood pressure) and when we translate that into words, it would be along the lines of “there’s VitD in milk” which is what A says.
Aren’t both A and B required for the physician’s conclusion to be “properly drawn”? If you don’t assume B, it is completely possible that milk contains some other substance that results in an increase in blood pressure and the stimulus clearly doesn’t limit a rise in blood pressure to calcium deficiency. Though technically even B isn’t really enough–it really should be that milk doesn’t contain any substance that is likely to cause an increase in blood pressure in older people that is equal to or greater than the decrease in blood pressure that would result from intaking the calcium content in the same amount of milk. First time I’ve ever found myself disagreeing with the LSAT test makers but I think this stimulus has two potential flaws and thus two assumptions that are needed. Unless I’m missing something in my reasoning.
This is a sufficient assumption question: required is irrelevant. It is very important to be crystal clear on this distinction. On sufficient assumption questions such as this one, we have to prove the conclusion right. But the answer need not be necessary.
Whereas on necessary assumption questions the answer is necessary, but need not prove the conclusion true.
Note: This is an old comment but I wanted to clarify the point.