Logical reasoning PrepTest 139 · Section 1 · Question 3

Incorrect. This answer is way too broad to serve as a weaken answer in bringing up that the study didn't ensure that every other aspect of the two groups' diet was the same. At most, the argument assumes that the two diets were similar enough in relevant aspects.

Incorrect. The argument is designed to draw a conclusion about a causal factor in cancer, not to make a recommendation. It's not a flaw to fail to draw a conclusion that the argument might justify but isn't the point of the argument.

Incorrect. This answer can feel as if it's raising alternative causes, and it is. But in order to weaken the argument, the answer would have to suggest that there's an alternative cause to the cancer in this study, not that there are alternative causes in general. This answer even concedes that galactose can increase cancer risk ("that can increase"), which would seem to accept the conclusion as true.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Sample - People who ate about the same amount of yogurt, while some developed cancer and others didn't
Results - Those who developed cancer had a lower level of an enzyme that helps digest galactose (in yogurt)
Conclusion - Too much galactose causes cancer

Answer Anticipation:
This argument starts by noting that it's going to base its conclusion on the results of a study, so we should start by considering a sampling flaw and a correlation/causation flaw.

The argument notes that it looked at groups that had recently developed cancer and hadn't, trying to find a relevant difference between the groups. There's no reason to believe that these groups were unrepresentative or skewed in a particular way, and this is one valid way to run a study, so there's no clear sampling flaw here.

However, the argument does reach a causal conclusion. And that's based on a correlation—the group that developed cancer also lacked a certain enzyme and thus had more galactose in their system. That's a jump from a correlation to causation. It's possible that it's not the galactose that caused the cancer, but rather something else that caused both the high galactose levels and the cancer (e.g., that enzyme might directly cause cancer). In ignoring potential alternative causes, this argument is flawed.

Since we are asked to weaken this correlation/causation flaw, we can look for a common answer:

(1) ID an alternative cause (as we already discussed)
(2) ID counterexamples (groups without the enzyme who don't have cancer)
(3) Reverse causality (cancer reduces the enzyme/increases galactose levels)

Answer Explanation:
This answer brings up the possibility of reversed causality, which is one method of weakening a correlation/causation flaw.

Key Takeaway:
Weaken questions quite frequently deal with correlation/causation flaws—especially when a study or survey serves as the basis for the conclusion. When that happens, look for answers that bring up alternative causes, counterexamples, or suggest that the causality in the conclusion is reversed.

Incorrect. This piece of information wouldn't affect the argument since there's a general correlation between the relevant elements.