PrepTest 124

Incorrect. If anything, this lines up with the conclusion that is suspicious of the effects of night-lights on eyesight.

Incorrect. This answer rules out reversed causality, which would strengthen an argument that reached a causal conclusion. That's the opposite effect we're looking for and this argument doesn't reach a causal conclusion—two reasons to eliminate it.

Incorrect. This aligns with the conclusion that any nearsightedness caused by night-lights would not persist into older ages.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Study 1 - Children who slept with night-lights as infants were more likely to be nearsighted
Studies 2 and 3 - Children who slept with night-lights as infants weren't more likely to be nearsighted
The children in studies 2 and 3 were older
Conclusion - If night-lights were the cause of nearsightedness in Study 1, then that effect disappears with age

Answer Anticipation:
This argument doesn't rely on one study, or two studies, but rather three studies. As when an argument relies on a single study, we should consider a sampling flaw, and a correlation/causation flaw. However, since there are multiple studies and the conclusion is more in line with the results of the latter two, we should also consider if sufficient evidence is given to go with those studies over the other.

Starting with the sampling flaws, we're told that it was of children who slept with night-lights as infants and those who didn't. That's a comprehensive sample (you either did sleep with one or you didn't), so there's no reason to question the representativeness of it for that reason. It doesn't go into the sizes of the samples, so that's unlikely to be correct, but if the answer brings up a too-small sample (most likely with the latter two, since it relies on them to reach the conclusion), that could be correct.

Second, we should consider a correlation/causation. However, we can quickly rule it out since the conclusion states that something isn't the cause of a given effect. While the conclusion sounds causal, it's actually saying that night-lights aren't a cause of long-term nearsightedness, if they're even a cause of short-term eyesight problems.

Finally, we have to consider if there's reason to side with the latter two studies over the former. However, in this case, based on this conclusion, it does give reason to side with the latter two studies. It gives additional information—the different ages of the children in the studies—to provide context that allows for those studies to hold more weight about the long-term effects of night-lights.

So we're left with essentially one avenue to weaken this argument—question the sample, most likely by highlighting a sample size issue. It's uncommon that that happens without some hint of it in the stimulus, but it's all we're left with.

Answer Explanation:
This answer highlights a sampling flaw in the latter two studies, which are crucially relied on by the Doctor to reach the conclusion that any effect of night lights disappears with age. In stating that the sample was too small to allow for any conclusion to be drawn, the argument undermines an argument that concludes something on that sample.

Key Takeaway:
When an argument relies on a study, there's a good chance that there's a sampling flaw, or a correlation/causation flaw. When neither is explicitly present in the argument, there's a chance that the correct answer will add in information that establishes the flaw was present. This is almost always going to establish a sampling flaw, as it's easy to add information about a sample size or representativeness, but much harder to insert a correlation/causation flaw.

Incorrect. This answer is too weak to affect the argument. The argument is statistical, talking about general trends across a population, which allows for a few outliers from the average.