Logical Reasoning

PT151 · S3 · Q20 The level of triglycerides in the blood

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The level of triglycerides in the blood rises when triglycerides are inadequately metabolized.

Conclusion (thus)

It is likely that consuming large amounts of fat, sugar, or alcohol (things that increase triglyceride levels in blood) is a factor causing heart disease.

Evidence

Patients with blood triglyceride above 1mg / mL are twice as prone to heart attacks as others.

Evaluate

Our Conclusion is causal, X is a factor causing Y

and our Evidence was a correlation People with trait X are twice as prone to be trait Y

so we know we're in the world of Explain Curious Fact:

Curious Fact ... why is there a strong correlation between high blood triglyceride levels and heart attacks?

Author's Explanation ... the high blood triglyceride is causing the heart attack.

The author doesn't explicitly say that, but her conclusion implies that she is interpreting this correlation to mean that the blood triglyceride level was a causal factor in the heart attacks. That's why she's arriving at a conclusion that .

Whenever an author interprets a correlation between X and Y to mean that X causes Y, we want to consider two alternate explanations: - Reverse Cause (what if Y causes X) - Third Factor (what X and Y are both attached to Z)

Here, that would mean, ? Or,

Goal

When we're doing Weaken and we come across an Explain Curious Fact type argument, the most typical form for an answer is to suggest an Alternate Explanation for the curious fact. The less typical option is to undermine the plausibility of the story the author is telling.

So let's primarily look for , or look for something that hurts the plausibility of the conclusion.

(We might suspect that the random first sentence is there for some reason. Are they going to use this metabolized fact in the correct answer?)

20.

Which one of the following, if true, most weakens the argument?

  1. People with a high-fat diet

    No Impact

    If we had evidence of high-fat diets being correlated with lower risk of heart disease, that would weaken the plausibility of the author's conclusion. But this answer doesn't say "people on high fat diets have a lower risk than those who aren't on such diets". It compares groups with two differences: "high-fat + heavy exercise" vs. "low-fat + little exercise". We can't draw any good conclusions when there are two variables changing. Which of the two variables accounts for the difference?

    25% picked this

  2. Triglyceride levels above 2 milligrams

    No Impact

    This conclusion is only about heart disease, so talking about other serious illnesses is pretty irrelevant. If anything, though, this answer may strengthen the plausibility of the author's causal story a little, insofar as it would show an example of high blood triglyceride increasing (i.e. influencing) the risk of other illnesses.

    3% picked this

  3. Shortly after a person ceases

    No Impact

    This doesn't strengthen or weaken, but it's very compatible with what we already heard. We know that consuming alcohol and processed sugar are known to increase triglyceride levels in the blood, so we would expect that if you ceased regularly consuming these things, your triglyceride levels would go down.

    3% picked this

  4. Correct

    Heart disease interferes with the

    Why this is right

    This does what we expect Weaken correct answers to do when an author presents a correlation and assumes one possible causal explanation for it: it provides an Alternate Explanation for the correlation. This is the Reverse Cause explanation. High blood triglyceride isn't correlated with heart disease / heart attacks because the high blood triglyceride causes the heart disease. Instead, this answer suggests, they're correlated because heart disease causes the high blood triglycerides. After all, heart disease causes the body trouble with metabolizing triglycerides, and the first sentence tells us that when we can't metabolize triglycerides, it raises our blood triglyceride level.

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

    67% picked this

  5. People who maintain strict regimens

    No Impact

    If anything, this very mildly strengthens the author's case by corroborating that avoiding fat / alcohol / sugar is associated with health. But what people tend to do for their health doesn't really help us analyze whether these substances specifically impact heart disease risk.

    1% picked this

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