Q10 - A large group of hyperactive

[cyruswhittaker]

Can you help me to more explicitly understand the flaw here? I am not fully certain why B is correct.

[ManhattanPrepLSAT1]

The flaws committed in this argument are several. The biggest and most direct flaw is that the argument mistakes correlation for causation, but unfortunately as you read through the answer choices, you don't see that anywhere.

After reviewing the answer choices though, an argument for one of them is the only one possible. Answer choice (B) says that the argument forgot to assemble a control group. In a way, this addresses the causation issue. Without a control group we cannot be certain that the changes in behavior were actually the result of the low additive diet when in fact they could be the result of some change in the environment, like more structure at home or the children went back to school, etc.

It makes sense that you would want a control group as well. You wouldn't claim that a certain medication has certain affects without testing it in studies that contain control groups.

(A) is irrelevant. Proportionality was never claimed in the conclusion.
(C) is irrelevant. The number of children exhibiting behavior problems is never implied, concluded, or discussed - just the percentage of children.
(D) is too narrow. The argument is much broader than the behavior of "some" children.
(E) is too narrow. The argument is much broader than the behavior of "some" children.

I hope this helps clear this one up. If you still need some more help with it though, please let me know!

[manoridesilva]

I was stuck between B and E. E seemed a bigger flaw to me for the following reason:

If 60% of the children originally had problems, then the remaining 40% didn't. After the diet change, 30% had problems, ie 70% didn't. Because we don't know if those who had problems originally were the same children who ceased to have problems after the change, it's entirely possible that the 30% who had problems after taking the low-additive diet (LAD) were part of the 40% who had no problems on the high-additive diet (HAD). In other words, the LAD could have created problems where none previously existed. I felt this highlighted a major problem.

That said, is another reason to dismiss E (other than it being too narrow as you said) that, even if the LAD made things worse in some children, answer E doesn't mention where HAD fits in?

[ManhattanPrepLSAT1]

That said, is another reason to dismiss E (other than it being too narrow as you said) that, even if the LAD made things worse in some children, answer E doesn't mention where HAD fits in?

See how the argument isn't about absolutes. It doesn't say that everyone who has a low-additive diet will have better behavior than those with a high-additive diet. Instead it speaks in percentages. So it's okay if there is an outlier that conform to the average improvement.

If the argument would have concluded an absolute relationship between low-additive diets and improved behavior, answer choice (E) would have been a correct answer. But the conclusion suggests that low-additive diets are merely "contributing to behavior."

And another way you can think of what answer choice (B) is saying, is that the argument doesn't provide a control group. Usually when you conduct studies to test medicines or procedures, the study uses a control group (a set of members who receive a placebo).

[emily315]

Why is E not ok?

[krishna.kilambi]

I thought frequency with which children exhibit behavioral problems is irrelevant to the question. The evidence is about the 60% who exhibit behavioral problems compared to only 30% who exhibited it after a low-additive diet and that's the reason I believe E is irrelevant.

Correct me if I am wrong.

[maryadkins]

I agree that "frequency" throws a new layer of confusion on this problem. But I would more readily be willing to dispense with (E) because of what Matt noted (and which you're getting at, too, here): This question is about percentages of children, and (E) is only about "some." Those could be two kids, a number that would hardly throw off the claim being made. We don't know what "some" means, and it could be very few. For this reason, (E) doesn't really impact the problem, whether "frequency" is irrelevant or not.