Logical reasoning PrepTest 130 · Section 1 · Question 20

Incorrect. The stimulus notes that type B volunteers had their lipid profiles unchanged, while many type A volunteers had their lipid profile shift to type B. It's lipid profile that's tied to heart disease, so, if anything, the argument supports that heart disease risk increased overall in the study.

Incorrect. Cholesterol levels for type A volunteers are never discussed, so this answer is out of scope.

Incorrect. The stimulus never attributes the diet to change, just noting that they coincided, so the causal relationship of any change is out of scope of this stimulus.

Incorrect. Similar to (C), the argument only discusses correlations and outcomes, not causality, so this answer is out of scope.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
Type B heart disease risk is higher than Type A.
Study: Type A and Type B volunteers put on a low-fat diet.
Type B—Cholesterol down, lipid profile the same
Type A—No benefit from diet, some shifted to Type B

Answer Anticipation:
First important thing to note—the argument discusses some changes and some correlations, but it never uses causal language. As such, any answer that brings up a causal relationship is likely a trap, as the human brain likes to read causality into correlations.

Second thing to note—there isn't a lot of overlap in this information, but there is one. We learn that some Type A volunteers shifted from to Type B, and that Type B people have a higher risk of heart disease than someone with a Type A profile. For this group, then, their risk of heart disease has increased.

Finally, there are comparisons between Type A and Type B volunteers here. Comparisons frequently lead to inferences, so we should have that information clearly lined up.

Answer Explanation:
Those with type B lipid profiles have a higher risk of heart disease than those with type A, and some of the type A volunteers shifted to type B during the study. For at least those volunteers, the risk of heart disease must have increased, so this answer is supported.

Key Takeaway:
Must Be True questions frequently rely on you to put together overlapping pieces of information. It's how to make inferences in LG, and it's a great place to look for inferences in LR. Comparisons, as well, frequently lead to inferences. Here, the overlap between two comparisons (Type A volunteers before and after the diet change; Type A vs. Type B heart disease risk) led to the correct answer.