PrepTest 130, Section 3, Question 23
Many scientific studies have suggested that taking melatonin(46 more words not shown)
Which one of the following,(6 more words not shown)
- AA weaker correlation(25 more words not shown)
- BNone of the(19 more words not shown)
- CIn the studies(16 more words not shown)
- DSeveral people who(14 more words not shown)
- EIf melatonin were(22 more words not shown)
Reading the argument
A treatment that helps some people fall asleep might not help people with insomnia. Their difficulty sleeping could involve a problem that the treatment doesn't address. So the author's cautious opening makes sense: evidence that melatonin can induce sleep isn't automatically evidence that it treats insomnia.
Most of the studies excluded people with insomnia, and many found significant effects in only a few subjects. That limits what we can learn about insomnia, but it doesn't establish that melatonin never helps it. Some studies may have included people with insomnia, and the few responders might have included them.
What we’re looking for
What I'd want to see is what happened when people with insomnia actually received the tablets. For this strengthen question, evidence about that group's response could make the author's caution much better supported. We shouldn't substitute a claim about people in general for the group the conclusion concerns.
Working the answers
- A
This offers some support: studies including people with insomnia found a weaker association between melatonin and sleep. But those studies could contain both kinds of subjects, and the overall association doesn't tell us exactly who responded. C gives a more direct result for the people with insomnia, making it the stronger answer.
- B
A sample needn't represent the entire human population to provide useful evidence about insomnia. The important issue is whether the study gives us relevant information about people who have that condition. An unrepresentative sample could still include a useful group of those patients; B doesn't identify the relevant defect.
- CCorrect
In the studies that included people with insomnia, the significant effects occurred only among people without it. That directly addresses the group we needed to examine. The study results supporting sleep induction came from the people without insomnia, so those results give less reason to conclude that melatonin helps treat insomnia. C doesn't establish that no person with insomnia could ever benefit; it strongly supports the author's warning about what these studies show.
- D
Some placebo recipients reporting better sleep doesn't tell us how the subjects with insomnia responded to melatonin. It also doesn't compare the size of the placebo response with the treatment response. Those reports could occur while melatonin still had a meaningful effect for the relevant patients.
- E
This rule would help us reject effectiveness if we knew of a person with insomnia who took melatonin and was not significantly affected. But the passage only says that few subjects responded, not that few subjects with insomnia responded. All the subjects with insomnia could be among those few responders. Without identifying a nonresponding person in that group, the rule doesn't give the support C provides.
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