Logical reasoning PrepTest 151 · Section 3 · Question 20

Incorrect. This answer changes up two factors—exercise and diet. Since both change, we can't be certain which (if either) lead to the change in heart disease, and that uncertainty lets us eliminate this answer.

Incorrect. The conclusion is about heart disease, so this conclusion about other illnesses is out of scope.

Incorrect. While this answer doesn't connect triglycerides or diet to heart disease, it does strengthen the statement that diet affects blood triglyceride levels, although this was already presented as a premise. By aligning with the argument, this answer, if anything, strengthens it.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
A blood triglyceride level over a certain point is correlated with increased risk of heart attacks, so eating foods that increase blood triglyceride levels will cause heart disease.

Answer Anticipation:
If you couldn't tell from the language in our Stimulus Summary, this argument has a correlation/causation flaw going on. In general, there are three ways to weaken a correlation/causation argument: 1) present an alternative cause; 2) find counterexamples (cause without effect, or effect without cause); or 3) reversed causality.

When the conclusion is about an increased risk, or a causal factor, instead of a primary cause, counterexamples are less likely to be correct. When the subject is medicine, reversed causality is correct a disproportionately large amount of the time when it makes sense. Here, as far as we non-doctors know, it's possible that heart disease causes high blood triglyceride levels. Let's look for that while staying flexible in case the answer falls into one of the other patterns.

Answer Explanation:
This answer brings up the reversed causality we anticipated. If heart disease makes it harder to metabolize triglycerides, the causality is the opposite of what the author argues, thus weakening the argument.

Key Takeaway:
Weaken questions that deal with medical topics frequently have an answer that reflects reversed causality.

Incorrect. This answer doesn't mention whether these people do or do not have heart disease, making it hard to analyze the impact it has on the argument, and can thus be eliminated.