#19 - Recent studies have demonstrated that smokers are

[Administrator]

Complete Question Explanation

Weaken-CE. The correct answer choice is (A)

Because smokers are more likely to drink caffeinated beverages, and also more likely to develop heart disease than non-smokers, the author concludes that there is a positive correlation between heart disease and caffeine consumption. This is not a terribly weak argument, since the author does not go so far as to suggest that drinking coffee causes heart disease: on the contrary, she explicitly refutes that hypothesis. A positive correlation between two variables only requires that the two are directly associated: in other words, the more likely one is to drink coffee, the more likely she is to develop heart disease, and vice versa.

To weaken the positive correlation between heart disease and coffee, we need to think of ways to show that drinking coffee is either negatively correlated with the development of heart disease, or not correlated at all. To do this, we need to remember that neither the study linking smoking to increased caffeine consumption, nor the study linking it to heart disease, considered what effects, if any, caffeine consumption has on the development of heart disease itself. For instance, it is entirely possible that smokers who drink coffee have lower incidence of heart disease than smokers who do not, even if smokers in general are more likely to develop heart disease than non-smokers. If caffeine mitigated the ill effects of smoking and improved cardiac health, then heart disease and caffeine consumption are negatively correlated, i.e. the more likely one is to drink coffee, the less likely she is to develop heart disease.

Answer choice (A): This is the correct answer choice. See discussion above.

Answer choice (B): Even if something else is a more important factor in the development of heart disease, the correlation between drinking caffeinated beverages and heart disease still stands. Remember: you are not trying to weaken a causal argument, as the author never said that drinking coffee causes heart disease. This is a Shell Game answer and is incorrect.

Answer choice (C): This answer does the exact opposite of what is needed: it strengthens the argument and is therefore incorrect.

Answer choice (D): If the positive correlation is observed only among a particular subset of the population, this does not weaken the notion that such a correlation actually exists. If, on the other hand, answer choice (D) had also shown that caffeine consumption and heart disease are negatively correlated in the general population, this would have been a far superior answer.

Answer choice (E): Even if there is a common cause for both the development of heart disease and behaviors such as drinking caffeinated beverages and smoking, the correlation observed earlier still holds. In fact, the presence of a common cause (let's say, neurotic personality) can further reinforce the positive correlation between these variables and strengthen the argument. This answer choice is incorrect.

[prep88]

Hi everyone,

I don't understand why is this question is a Weaken question and not Flaw, because a lot of flaw questions are worded like this?

Thank you!

[Dave Killoran]

Hi Prep,

Good question! The question stem we're looking at is as follows: "The argument’s reasoning is most vulnerable to criticism on the grounds that the argument fails to take into account the possibility that..." The reason this is a Weaken question is because of the phrase "fails to take into account the possibility that..." This means there's a specific scenario that, when raised, will weaken the argument. In other words, they want some sort of specific situation that relates to the topic in the stimulus that will undermine the argument. Had they left it more vague, then it would have been a Flaw question because the answer could then be posed in more abstract terms. A question stem like that would look very similar but not reference the specific scenario, and read something like this: "The argument’s reasoning is most vulnerable to criticism because..." That's a subtle difference, but definite enough that when the question stem references a specific scenario, we classify it as Weaken.

Of course, Weaken and Flaw are very closely related, so if you didn't classify this perfectly, it wouldn't hurt you.

Please let me know if that helps. Thanks!

[prep88]

This is invaluable! Thnks!

[adlindsey]

I see why A is right. While I see how D could strengthen the conclusion, wouldn't it also weaken it, since it brings an alternative cause by stating, "it is only among people who have a hereditary predisposition to hear disease..."? I thinks I understand why it's not correct, but maybe another explanation would help. Thanks.

[Adam Tyson]

Thanks for the question, adlindsey. While answer D, if true, would lessen the positive correlation between caffeine and heart disease, it would not eliminate it completely. Answer A, however, would - it would turn the correlation into a negative one instead of positive. That's a much more powerful attack on the argument! That's what makes A the best answer of the two.

Hope that helps!

[Tomars]

Hi!

I'm still very confused about this one. I don't think I've ever felt more stuck about an answer that felt (and still feels) obvious and is apparently wrong.

A says smokers who drink CB are less likely to develop heart disease than are smokers who do not drink CB. This doesn't eliminate the positive correlation at all between CB and heart disease; it simply divides the group of smokers by whether they drink CB and tells us smokers who do not drink CB do not have as strong a positive correlation (if one at all) compared to those who drink CB. This still leaves lots of room for a positive correlation among smokers who drink CB, albeit one that is not as strong as smokers who do not drink CB.

D, however, seems to eliminate the positive correlation altogether between CB and heart disease. By telling us that only those caffeine drinkers with a hereditary predisposition to heart disease actually show a positive correlation with heart disease, B is saying those smokers who drink CBs and are not genetically predisposed show either no correlation or negative correlation to heart disease.

Thank you so much!

[Tomars]

Hi there,

I've revisited this question couple of times and still can't seem to understand why the correct answer is correct. Is there a chance someone is able to provide an explanation countering my reasoning above?

Thank you!

[AthenaDalton]

Hi Tomars,

Thanks for your question!

Answer choice (A) eliminates the positive correlation between drinking caffeine and developing heart disease since it demonstrates that caffeine consumption actually decreases a smoker's risk of developing heart disease. When two variables are inversely related in this way, we can describe them as being negatively correlated.

Just for the sake of example, we can say that two variables are positively correlated when an increase in one variable makes the other increase. So the number of hours I work is positively correlated to the size of my paycheck: more hours leads to higher pay. By contrast, the number of meals I purchase is negatively correlated to the size of my bank account: an increase in the number of meals purchased leads to a lower bank account balance.

In the group of smokers who drink caffeinated beverages, there is a negative correlation between the first variable (drinking caffeine) and the second variable (developing heart disease). The smokers who drink caffeine are less likely to develop heart disease than smokers who abstain from caffeine.

You mentioned that there's still a positive correlation between smokers who don't drink caffeinated beverages and developing heart disease. The only positive correlation for this group is between smoking and heart disease. If this group doesn't consume caffeine, we can't say that their caffeine consumption is related to heart disease ... because they aren't drinking caffeine at all!

The reason that (D) is not as good of an answer as (A) is that answer choice (D) still demonstrates some positive correlation between caffeinated beverages and heart disease. In (D), we know that people who have a genetic pre-disposition to developing heart disease who also drink caffeinated beverages will increase their risk of getting heart disease. The link between caffeine and heart disease is weaker (since it apparently only applies to a small subset of the smoking population), but it's still there. For at least some smokers, drinking caffeine will increase their risk of getting heart disease. So in answer choice (D) there is still some positive correlation between the two variables.

I hope this helps clarify things for you. Good luck studying!

[cinnamonpeeler]

Thank you for the explanations. I just need some clarification about correlation and causation.

The conclusion of this argument is that there exists a positive correlation between drinking caffeinated beverages and the development of heart disease. How do we know, from that statement alone, that the positive correlation is such that if you drink more caffeine you are more likely to get heart disease. Couldn't that statement also be read as if you get heart disease, you are more likely to drink caffeine? Are we using the context of the argument to assume that the former reading of the positive correlation is what the speaker intended, and not the latter?

And a more general point: how should we understand the relationship between correlation and causation? When we know that x causes y, can we also say that x is correlated with y? And whether this correlation is positive or negative depends on the causal relationship, doesn't it? So, if the causal claim were that "smoking causes heart disease," we also know that there is a positive correlation between smoking and heart disease. On the other hand, if the causal claim were that "watching TV leads to worsened intelligence," the correlation would be a negative one such that the more TV that you watch, the less likely you are to be intelligent?

What about when a reduction in size of one variable leads to a reduction in size of another variable, or a reduction in size of one variable leads to an increase in size of another variable? What do we call these? Can they still be understood in the language of positive and negative correlation?