PrepTest 122

Incorrect. This answer explains how the causality works. If HDLs cause the body to excrete cholesterol, and cholesterol is a causal factor in heart disease/stroke, then it makes sense that HDL will lower the risk of those diseases.

Incorrect. The stronger two things are correlated, the more likely they're causally related. Here, in bringing up a subset of the population where lower HDL levels and higher risk of heart disease/stroke are correlated, the conclusion that HDL is a causal factor in lowered risk of heart disease/stroke is strengthened.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Bizarro Strengthen

Stimulus Summary:
Cholesterol is a causal factor in heart disease/stroke
Cholesterol requires lipoprotein (L) to get throughout the body
LDL - Increase risk of heart disease/stroke
HDL - Increased by aerobic exercise; are higher in women than men
Aerobic exercise and being female are correlated with lower heart disease/stroke risk
Conclusion - HDL probably helps prevent heart disease/stroke

Answer Anticipation:
This stimulus is all over the place! When there's this much details, we should start with the conclusion and then work backwards to see what is actually relevant.

The conclusion here is right smack dab in the middle—it even highlights itself by saying "we can tentatively conclude. . . " And that conclusion is that HDL helps to prevent heart disease and stroke. That's a causal conclusion in a Strengthen question, so we should start by considering a correlation/causation flaw.

So is the relationship between HDL and heart disease/stroke supported by a correlation? It is, but it's a bit more complex than that. Aerobic exercise causes an increase in HDL levels, and it also is correlated with a lower risk of heart disease/stroke. Normally, a causal premise can support a causal conclusion, but here, it's not the supposed cause and effect that are established in the causal chain. Instead, there's a jump in the causal chain that's bridged by a correlation. Aerobic exercise causes higher HDL levels and is correlated with lower risk of heart disease/stroke. Therefore, HDL and the lower risk are correlated (though aerobic exercise). For the other factor—being a woman—there's no causality there, just correlations. So both of the identified connections here are correlations, and thus we can strengthen this argument through the normal means:
(1) Eliminate an alternative cause
(2) More examples of cause and effect going together
(3) A "control group" where we see no cause/no effect
The details of this argument also bring two other anticipated answers into play:
(1) Rule out reversed causality, which would weaken the argument (it's possible that heart disease/stroke raise HDL levels)
(2) Explain the causal relationship—how do HDL levels lower risk of these diseases?

And what about the rest of the stimulus? While those statements may provide details that help analyze answers, they're not relevant to the logic itself, since cholesterol and LDL aren't directly mentioned in the conclusion. There's already enough going on in this question—let's not add more than is necessary!

Answer Explanation:
Without a medical degree, there's no way for us to know whether this means that they should increase or decrease cholesterol levels. If anything, it could be argued that this stuff sticking around in the bloodstream means that it's probably carrying around more cholesterol, which should increase the risk of heart disease/stroke since cholesterol is a causal factor in it.

Key Takeaway:
Causal premises can support causal conclusions, but the causality in the premises has to connect the terms that are said to be causally related in the conclusion. If there's a causal premise that "chains" with a correlation, then there can still be a correlation/causation flaw.

Incorrect. This answer is pretty direct—HDLs mitigate the health risks from LDLs, which include heart disease and stroke. This more or less states that the conclusion is right, which strengthens the argument.

Incorrect. This answer correlates higher HDL with lower risk of heart disease/stroke, strengthening the argument.