PrepTest 124, Section 1, Question 8
Doctor: In three separate studies, researchers compared children(70 more words not shown)
Which one of the following,(8 more words not shown)
- AA fourth study(22 more words not shown)
- BOn average, young(22 more words not shown)
- CIn a study(27 more words not shown)
- DThe two studies(26 more words not shown)
- EIn a fourth(29 more words not shown)
Reading the argument
How much can we trust those later studies? If each studied only five children, failing to find a pattern wouldn't tell us much about whether a real effect disappears with age.
All three studies concern children who slept with night-lights as infants. The difference is how old the children were when studied: the first group was younger. We aren't comparing infant exposure with first exposure as teenagers. The doctor's idea is that an effect of the earlier exposure wears off as children grow.
That is one possible explanation for the different findings. But perhaps the studies used small samples. Or perhaps the children in one study had much brighter night-lights. Those differences could matter without age making an existing effect disappear.
What we’re looking for
Notice the doctor's “if.” The conclusion doesn't insist that night-lights cause nearsightedness. It says that if they do, the effect fades. Arguing only that the cause might not exist misses that conditional claim. It's like answering “If magic were real, what would you do?” with “Magic isn't real.” For this weaken question, I want a reason to doubt that the studies establish the proposed fading effect.
Working the answers
- A
No correlation among infants doesn't show that an effect, if there is one, persists as children get older. The effect might become apparent later, or night-lights might not cause it at all. Neither possibility directly challenges the doctor's claim about what happens with age if there is an effect.
- B
This addresses whether already-nearsighted children are more likely to use night-lights. It doesn't tell us whether nearsightedness caused by infant exposure disappears later. Changing which children tend to use the lights doesn't resolve the question about the duration of a possible effect.
- C
Most children not becoming nearsighted doesn't establish that the lights have no effect. Imagine a rate increasing from 1 percent to 2 percent: most children would still not be nearsighted, despite an increase. C also concerns children who began using the lights later, rather than tracking the consequences of infant exposure. We lack the comparison needed to challenge the doctor's claim.
- DCorrect
The later studies examined too few children to support a meaningful conclusion about the causal relationship. Those are the studies the doctor relies on to infer that the effect disappears. If they couldn't reliably detect a relationship, their failure to find one gives us little reason to think it faded.
This doesn't prove the first study reliable or establish that an effect lasts forever. It undermines the particular evidence offered for the doctor's explanation.
- E
Some older children being nearsighted doesn't establish a lingering effect of night-lights. They might be nearsighted for other reasons. We need a comparison with older children who didn't have infant exposure, or other evidence tying the nearsightedness to that exposure. “Several” cases by itself doesn't supply that connection.
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