A large group of hyperactive children whose regular diets included food containing large amounts of additives was observed by researchers trained to assess the presence or absence of behavior problems. The children were ten placed on a low-additive diet for several weeks, after which they were observed again. Originally nearly 60 percent of the children exhibited behavior problems; after the change in diet, only 30 percent did so. On the basis of these data, it can be concluded that food additives can contribute to behavior problems in hyperactive children.

The evidence cited fails to establish the conclusion because

(A) there is no evidence that the reduction in behavior problems was proportionate to the reduction in food-additive intake

(B) 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

(C) exactly how many children exhibited behavior problems after the change in diet cannot be determined, since the size of the group studied is not precisely given

(D) there is no evidence that the behavior of some of the children was unaffected by additives

(E) the evidence is consistent with the claim that some children exhibit more frequent behavior problems after being on the low-additive diet than they had exhibited when first observed

Please explain your answer

Another vote for B.. as it shows other reasons for behavioral problems
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Brainless

It is not as important to know exact numbers of children w/reduced behavioral problems (you are given percentages so you already know that there was a relative decrease in behavioral problems) as it is to know that the decrease in behavioral problems cannot be attributable to something outside the diet change.

A control group (the lack of which is what choice B cites as the problem with the study) is necessary to establish that the diet change was not due to a factor external to the study.

But there is no evidence for E. 60% had behavior problems before the diet, but only 30% had behavior problems after the diet. While some children may indeed have increased behavior problems after the diet, there is no evidence of that, and overall, behavior problems decreased.





B is correct in that there was only one group of children studied. It's true that this one group was evaluated before and after the diet change... but a a second group should be studied during the same time period that does not undergo a diet change. What if the school implemented a new discpline system during the study? If you only evaluated one group, you might attribute the decrease in problems to the diet change. But if you looked at two groups (one with a diet change and one without), and there were similar decreases in behavior problems, you wouldn't be as quick to say the decrease was due to a diet change. (In fact it would seem the decrease was due to the new discipline system.)