Logical reasoning PrepTest 131 · Section 1 · Question 8

Incorrect. Even if only one was widely suspected of making hyperactivity worse, others still could potentially be a cause of it. The expectations don't determine the reality, so this answer choice is out of scope.

Incorrect. While not supported by the argument, this answer aligns with the conclusion of it, so it doesn't weaken it.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Study: Children with ADD were split up into 4 groups. 3 were each given a different sugar; the 4th was given a sugar substitute. There was no difference in their behavior.
Conclusion - Sugar doesn't make the hyperactivity associated with ADD worse.

Answer Anticipation:
This argument describes a study with more groups than we're used to! There are usually two, maybe three groups—this has 4.

Whenever a study is performed, we should consider a sampling flaw, and a correlation/causation flaw. However, there's no reason to believe that the children selected for this study were unrepresentative, and the conclusion is that one thing didn't cause another, so these two common avenues are unlikely to lead to a correct answer.

However, knowing what we know about studies, there's another issue we can highlight here. While the argument does state that a "control" group was used, the way it's described actually precludes it from being a control! The control group should not have a change that the other groups do. Here, the control group didn't get a sugar, but it does feature a separate change—they're given a sugar substitute. That throws the "controlled" nature of the experiment off because that group also had a change, and thus that change could have led to the same effect. If sugar substitute also exacerbates hyperactivity in children with ADD, then the conclusion here falls apart.

So let's find an answer pointing out that the control group isn't a control group at all, thus weakening the experiment.

Answer Explanation:
This answer highlights the issue with giving the control group sugar substitute instead of their normal diet. If these substitutes also cause hyperactivity, then comparing the experimental groups against the control group would show no differences, despite there actually being an across-the-board change in each group.

By undermining the legitimacy of the control group, this answer weakens any conclusions drawn from the experiment.

Key Takeaway:
The whole point of a "control" group is to not make any changes from the baseline in it, so that there's a point against which the changes made for the other groups in the study can be measured. If the "control" group has a change made to it, the experiment is no longer under control!

Incorrect. In an experiment with a true control group, putting the children in these environments could be measured against the baseline, so there's no problem with designing an experiment that has stimuli meant to elicit a certain response for testing purposes.

Incorrect. Without establishing that any of these children were in the study, or that knowing this information affects behavior, this answer choice is out of scope.