Q24 - Physician: The rise in blood pressure

[LSAT-Chang]

I incorrectly chose (C) on this one... can somebody please help explain why we need to assume (A) and not (C)??? Wouldn't we obviously have to assume that one glass of milk doesn't contribute to a deficiency in the active form of vitamin D since that is what frequently causes the calcium deficiency??????????????

[houngkevin]

Hi, so this is my first response but since this forum has helped me so much I have decided to contribute. I actually chose C as well and it wasn't until closer observation I understood my mistake.

So if you read the premise carefully this is not merely a correlation problem but one of causation. Correlation is quite strong logically so there are many assumptions which must be made.

Anyway, I diagrammed "The rise in blood pressure that commonly accompanies aging often results from a calcium deficiency."
as

C-----> E
calcium deficiency (CD) ----> rise in blood pressure (RBP)

the next line also presents another causation element

deficiency in Vit. D (VD) ------> calcium deficiency (CD)

The conclusion is basically if you get rid of the calcium deficiency you get rid of the rise in blood pressure. No cause = no effect. Since the LSAT assumes that there is only one cause for that specific effect and no other cause will cause that effect. This is therefore quite a strong statement because it says that calcium deficiency is the ONLY cause of a rise in blood pressure. And that no other cause will cause this.

Now to analyze this...
The conclusion makes sense if there isn't a cause there's no effect. However, there is one precondition. The Vitamin D deficiency which leads up to the calcium deficiency must not be present as well. As you recall we had two causation statements. Therefore if we had the vitamin D deficiency needed for the body to absorb calcium then our conclusion would be false.

Also, notice the wording in the question stem, The conclusion is properly drawn if... This is not a necessary assumption question but instead a sufficient assumption. Thus the answer must be able to prove the conclusion completely.

C) doesn't prove the conclusion completely. Even if drinking the milk doesn't cause a deficiency in Vitamin D. Simply old age may contribute to a natural Vitamin D deficiency. Therefore, old people would still not be able to lower their blood pressure by drinking milk.

I hope this helps!

[noah]

Great explanation! Thanks for giving back to the forum community.

This one had my head spinning, so I'll take a crack at it too, and try it without using a formal diagram:

The conclusion is that some older people can lower their blood pressure by drinking milk. Why?

Because the milk can provide the calcium they need. And, we learn that blood pressure rising is often because of a calcium deficiency.

However, there's information about the deficiency too! It's caused by a deficiency of vitamin D, which is needed to absorb calcium. My goodness.

So, it seems OK to say that drinking milk can help some older people's blood pressure, but what about that nagging vitamin D deficiency. What if the milk doesn't address that. Sure, they get lots of calcium, but will they be able to absorb it? If so, we're good! (And notice that the conclusion is rather "soft" as it sticks with "some" older people, not all.)

So, (A) solves this issue and is sufficient. The milk, it tells us, has enough of the vitamin D to have the body absorb the calcium in that milk.

(B) is tempting, because we need to assume that. But, it doesn't help us with the vitamin D deficiency issue.

(C) is similar to (B) - we need to assume that the milk doesn't make the absorption issue even worse - but it doesn't assure us that the absorption issue is cleared up.

(D) is another tempting answer, but we don't know if the milk contains a "high" quantity of calcium, and we don't know if these folks are getting the "other substances needed..."

(E) is linking things that don't need linking! We already know that a vitamin D deficiency can cause a calcium deficiency, it's not important to know if that causation always occurs. Is drinking milk going to solve all of this is the real question at hand!

[zainrizvi]

Interesting Q - I've often seen sufficient answer choices as traps in necessary assumption qs, but never the other way around.

[shirando21]

I misread the question type, I thought it was necessary assumption.
That's why I thought C is necessary, A is not necessary, especially any other substances needed in order for the body to absorb the calcium in the milk.

[griswald]

Can someone please answer this question with a diagram? It looks like the conclusion is making a reversal of one of the premises.

[maria487]

Are B and C necessary--or are they almost necessary assumptions?

The reason why I ask is because they are both sweeping statements made for a conclusion that is qualified for only "some" older people.


Thanks for your help!

[dhlim3]

Can someone please answer this question with a diagram? It looks like the conclusion is making a reversal of one of the premises.

I would say that since this is a Causation problem, you will need a Causation diagram (as opposed to conditional).

The first two sentences of the stimulus would be written as:

Deficiency in Vitamin D needed in order for body to absorb calcium -> Calcium Deficiency -> Blood Pressure Rise

This translates to "Deficiency in Vitamin D needed in order for body to absorb calcium CAUSES Calcium Defiency, which CAUSES Blood Pressure Rise." (Note, if this was a conditional statement, it would translate to something vastly different).

Next statement: "Since the calcium in one glass of milk per day can easily make up for any underlying calcium deficiency"

This can NOT be written in either causation or conditional form because it does not contain any term that signifies either.

But the next part (the conclusion: "Drinking milk can lower blood pressure") contains a causation term ("lower") , so this can be written as:

Milk -> Blood Pressure NOT Rise (Or, for the sake of this particular argument, lower blood pressure).

Since this is a Causation argument, we need to show that the absence of cause results in the absence of effect in order to make this argument logically sufficient. Hence, the correct assumption will effectively link "Drinking Milk" with the "Negated" version of the causation chain written above (not really a negation because it's really showing absence of cause and absence of effect) , like this:

Milk -> NEGATE Deficiency in Vitamin D needed in order for body to absorb calcium -> NEGATE Calcium Deficiency -> NEGATE Blood Pressure Rise

In English, this translates to "Drinking milk PREVENTS the deficiency in Vitamin D needed in order for the body to absorb calcium, which in turn PREVENTS calcium deficiency, which ultimately PREVENTS the rising blood pressure (lowers blood pressure)".

Note: This does is not a mistaken negation since it's not a conditional statement. When you are trying to "prove" a causation, one way to do it is by showing that the absence of cause absolutely does not lead to its original effect.

Answer A correctly reflects this ("Containing enough of the active form of vitamin D" is just another way of saying "negating (or "curing") vitamin D deficiency")


Tell me if this sounds right.

[clementm284]

To tackle this question, I diagrammed it like this:

Blood pressure increase (upward arrow BP) --> Calcium deficiency (CD) --> lack of Vitamin D (-VD)

Contrapositive: VD --> -CD

Drinking Milk (DM) --> Make up for calcium deficiency (-CD)

Conclusion: Blood pressure decrease (downward arrow BP) --> Drinking milk (DM)

So we have this: (downward arrow BP) --> DM --> -CD

VD --> - CD

The correct answer would bridge drinking milk (DM) to bringing about Vitamin D (VD), in which A does just that.

I got this question correct but I'm wondering, is C a Necessary Assumption?

[sclw64]

I think there is another gap which needs to be filled.

Lack of vitamin D OFTEN(>50%) causes calcium deficiency, and lack of calcium OFTEN causes rise in blood pressure.

I understand it as most vitamin D deficiency accompanies calcium deficiency, and most calcium accompanies rise in blood pressure.

But how can you conclude some one with vitamin D has rise in blood pressure caused by it?

In other words, there is possibility that every calcium deficiency caused by the vitamin D deficiency is not the calcium that causes the rise in blood pressure.

Anh thoughts?