The conclusion of the argument is: "it can be concluded that food additives can contribute to behavior problems in hyperactive children." Why? "A large group of hyperactive children whose regular diets included food containing large amounts of additives was observed by researchers trained to asses the presence or absence of behavior problems." These children were then placed on a diet with low-additives and observed again. Originally nearly 60% of the children exhibited behavior problems, but after the change in diet, only 30% did.
What's the issue with the method of reasoning? The experiment had no constant. All the children underwent a change in diet so we cannot account for any outside variables that could have been affecting the children's behavior problems. It could be that being observed by researchers could have been the reason fewer children exhibited behavioral problems.
As such, it cannot be concluded on the basis of this data that food additives can contribute to behavior problems in hyperactive children. A constant must be present. Some of the children should have stayed on their high-additive diets, while the rest switched over to the low-additive diet. That way the only difference between the two groups would have been diet.
This is why answer choice (B) is correct. It clearly points out that "there is no way to know what changes would have occurred without the change of diet, since only children who changed to a low-additive diet were studied."
Hope this helped! Please let us know if you have any other questions.
knoxygirlMay 14, 2017
How would someone know this type of thing if they weren't familiar with study methods?
MehranMay 14, 2017
@knoxygirl not sure I am understanding your question here.
