Logical Reasoning

PT122 · S2 · Q11 Cholesterol, which is a known

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Cholesterol, which is a known factor in coronary heart disease and stroke, needs a carrier, known as a lipoprotein, to transport it through the bloodstream.

Conclusion (we can conclude)

HDLs help prevent coronary heart disease and stroke.

Evidence

Aerobic exercise increases one's levels of HDLs.

HDL levels are higher in women.

Aerobic exercise and being female are positively correlated with lower risk of coronary heart disease and stroke.

Evaluate

The author's conclusion is causal: HDLs help prevent coronary heart disease and stroke.

Was the evidence causal? Partly, yes. Aerobic exercise increases HDLs.

But partly, no. The final claim is a correlation: aerobic exercise is correlated positively with reduced risk of coronary heart disease and stroke, as is being female.

The author is thinking that the reason aerobic exercise / being female are each linked to lower risks of heart disease and stroke is due to HDLs.

The author is seeing both of these causal chains: do aerobic ⇢ higher ⇢ lower risk of exercise HDLs ? and stroke

being ⇢ higher ⇢ lower risk of female HDLs ? and stroke

Goal

We can strengthen this argument by ruling out alternate explanations for why aerobic exercise or being female are associated with lower risk of heart disease and stroke.

Or, we can strengthen by learning anything else that increases the plausibility that HDLs have this beneficial effect. Maybe HDLs are known to refuse to let cholesterol hitchhike its way through the bloodstream.

Let's get rid of four answers that strengthen this causal link (or rule out an alternative explanation).

11.

Each of the following, if true, strengthens the argument EXCEPT:

  1. HDLs, unlike LDLs, help the

    Strengthens Plausibility

    Since cholesterol is a known factor in heart disease and stroke, getting rid of cholesterol (as we find out HDLs uniquely do) could plausibly result in a lower risk of heart disease and stroke.

    4% picked this

  2. Persons who are overweight tend

    Strengthens Plausibility

    This provides more data points in which higher HDLs is correlated with lower risk of heart disease / stroke, and lower HDLs are correlated with higher risk of heart disease / stroke. The overweight people described in this answer tend to have low levels of HDLs and higher risk of heart disease and stroke. If an author is selling us on a causal relationship CAUSE EFFECT higher HDLs less risk of HD/stroke Then the most common way for LSAT to strengthen this connection is by giving us No Cause, No Effect data points, such as this answer.

    7% picked this

  3. Correct

    HDLs are less easily removed

    Why this is right

    This has no impact on the conversation, so it's our correct answer. Who cares about removing LDLs or HDLs from the bloodstream? Is anyone trying to remove either of those? Do we care then which is easier or harder to remove? Does being harder to remove from the bloodstream have any connection to lowering the risk of heart disease / stroke? Nope.

    Skill tested: Strengthen · how this choice captures the argument's function is the move to repeat next time.

    79% picked this

  4. A high level of HDLs

    Supports Plausibility

    (At least some of) the health risks associated with LDLs are higher risk of heart disease and stroke. If high HDLs mitigate that risk (i.e. lessen it), then high HDLs lessen the risk of heart disease and stroke. This answer essentially gives us the conclusion.

    3% picked this

  5. Men whose level of HDLs

    Supports by Ruling Out / Plausibility

    We might have argued that the connection between women, HDLs, and lower risk of heart disease / stroke is coincidental. Yes, women have higher HDLs on average, but that's not the reason they have lower risk of heart disease / stroke. Maybe there's some other characteristic of being a woman (f.e. higher levels of estrogen, better diet, looks better in a pair of Uggs) that is the reason that women have lower risk. This answer rules out those sorts of alternate explanations. "No, it's not the estrogen causing the lower risk. After all, if you look at men who have HDLs levels similar to those of women (but have less estrogen than women), you can see that they have lower risk of heart disease / stroke too." Even without talking through the alternate explanation angle, this answer on its face is showing more data points that correlate higher HDL with lower risk of heart disease and stroke, so on its own it also increases the plausibility of the conclusion.

    7% picked this

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