Logical reasoning PrepTest 142 · Section 4 · Question 18

Incorrect. The only action here that would fit into this answer is taking a melatonin supplement, and that was clearly intended here to cure insomnia/induce sleep—that's not an assumption.

Incorrect. While the Manufacturers are likely to be biased, it doesn't rely on their claim—it argues in favor of their claim based on a study. Since it doesn't take the claim for granted but rather offers support for it, this answer is wrong.

Incorrect. The only terms that are repeated are "pineal gland" and "melatonin," and it's hard to imagine what different meanings of those would be since one is an organ and the other a chemical.

Incorrect. This answer is the "reverses the causality" answer, but there's no reversal here—if there is a causal relationship, the melatonin cures insomnia, and there's no hint of a mistaken reversal.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Sample Ð 65-81 and suffering from insomnia
Results Ð Insomnia is substantially cured with melatonin, which is produced by the pineal gland
Manufacturers' claim Ð The pineal gland makes less melatonin with age
Conclusion Ð The Manufacturers' claim is correct

Answer Anticipation:
The argument is based on a study, so we should start by looking at a potential sampling flaw, and a potential correlation/causation flaw.

The sample here was those 65-81 and suffering from insomnia. Wow, that's a skewed sample. The conclusion is about the population generally, and this sample does not allow such a broad conclusion to be drawn. Specifically, the conclusion compares age groups, but it only studied those 65 and up, so that comparison is completely unsupported by the data collected in this study.

The argument here does have a causal conclusion (melatonin causes sleep/cures insomnia), but the study also establishes a causal relationship—insomnia's symptoms are stated to be "alleviated by" taking melatonin. That's a causal statement—rare in a stimulus based on a study!—and so we don't have a correlation/causation jump.

So we're left with that sampling flaw, so let's go look for it!

Answer Explanation:
The sample here only included those over 65 with insomnia. The conclusion was about something happening as one ages. Without a sample that includes younger people, that conclusion can't be drawn.

Key Takeaway:
When an argument features a survey, study, or poll, always check for a sampling flaw and a correlation/causation flaw first. They're the most common in a question with that feature!