Logical reasoning PrepTest 121 · Section 4 · Question 9

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Study - Several hundred female physicians showed an inverse relationship between two vitamins and heart disease
Conclusion - These two vitamins inhibit heart disease in women

Answer Anticipation:
Weaken questions tend to have correlation/causation flaws. Arguments that rely on studies/research tend to have correlation/causation flaws or sampling flaws. We should start our analysis there!

Let's start with the correlation/causation flaw. Does the study show a correlation? It does—it's an inverse correlation, but a correlation nonetheless. It's between low consumption of two vitamins and a higher level of heart disease. From that, it concludes that those two vitamins lower risk of heart disease. Since that's a jump from a correlation to causation, we can expect the normal weaken answers for an argument with that flaw:
(1) ID an alternative cause
(2) Counterexamples (though that's unlikely here since the argument is about a tendency, so a few people who fall outside the tendency
(3) Reversed causality (not as outlandish as it might sound—maybe heart disease makes someone naturally want to avoid food high in these vitamins)

For the sampling flaw, there's a large ("several hundred") sample. There is a shift from a discussion of "female physicians" and "women," so an answer highlighting a difference between all women and those who are physicians could serve as an answer here, but it seems unlikely that there's a difference between those groups as far as something related to medicine is concerned. Let's keep an eye open for an answer in this area without expecting it to show up in a manner that makes it correct.

Answer Explanation:
This answer raises an alternative cause. It's not that these vitamins are connected to heart disease, but rather the other nutrients in foods with them are causally related to heart disease. In bringing up an alternative cause, this answer weakens the argument.

Key Takeaway:
Weaken questions tend to have correlation/causation flaws. Studies tend to have correlation/causation flaws, and sampling flaws. Use these trends—and, in particular, the "double" likelihood of a correlation/causation flaw in a Weaken question with a study—to help quickly narrow down what you're looking for in an answer choice.

Incorrect. Since the conclusion is limited to discussing its impact on heart disease in women, this answer about the impact on men is out of scope.

Incorrect. This answer does highlight a difference between physicians and nonphysicians. However, it's not a difference relevant to the argument—knowing the link between diet and health doesn't impact what that health impact actually is.

Incorrect. If it was noted that the physicians had their diets changed as a part of the study, then establishing a baseline on heart disease would be important. However, the stimulus is completely aligned with a study where physicians were asked about their diet and any heart disease they've been diagnosed with, in which case there wouldn't need to be an advanced screen.

Incorrect. How rare certain vitamins are doesn't affect whether they're causally related to anything, including heart disease.