aragonn wrote:
Infant development researchers released a study recently that compared two groups of babies: those who were fed breast-milk during their first six months of life and those who were fed formula during the same period. The study's results showed that the group of infants fed breast-milk weighed significantly more on average at one year of age than did the group fed formula. The researchers concluded that a breast-milk diet leads to greater weight gain among babies than a formula diet.
Which of the following would cast the most doubt on the researchers' conclusion?
A. The mothers of infants in the breast-milk-fed group weighed significantly more on average than the mothers of babies in the formula-fed group.
B. Many of the infants in the formula-fed group at one year of age weighed more than the average weight of the breast-milk fed group at one year of age.
C. The average weight of the infants in the breast-milk-fed group was significantly greater than the average weight of the babies in the formula-fed group when the study began.
D. In controlled laboratory studies, a hormone found in breast-milk has been linked to increased weight gain in baby mice.
E. The average amounts of breast-milk and formula consumed by the two groups of infants over the course of the study were approximately equal.
Question Explanation
Conclusion: The researchers concluded that a breast-milk diet leads to greater weight gain among babies than a formula diet.
Premise: The study's results showed that the group of infants fed breast-milk weighed significantly more on average at one year of age than did the group fed formula.
Assumption: (1) It’s not a coincidence. It’s not a coincidence that the group of infants fed breast milk weighed significantly more on average at one year of age than did the group fed formula
(2) There’s no other cause. There’s no other cause for that one group of infants weighed more than the other group than that the first group was fed breast milk and the second group was fed formula.
This is a weaken question, as evidenced by the question asking to cast the most doubt on the study’s conclusion. The passage uses a causality pattern, stating in the conclusion that certain diets lead to greater weight gain in infants. The researchers concluded that a breast-milk diet leads to greater weight gain among babies than a formula diet. The two groups of infants were fed different types of food, and results showed that the group of infants fed breast-milk weighed significantly more on average at one year of age than did the group fed formula. The two standard assumptions of a causal reasoning argument are that the results are not a coincidence and that there is no other cause for the results. Because this is a weaken question, the correct answer choice could provide a counterexample to show that the results may be a coincidence. The weight difference may be unrelated to the consumptions of different foods. The correct answer choice could also provide an alternate cause for the results. A factor other than food consumption may explain the differences in weights between the groups. Evaluate the answer choices, looking for one that reflects these ideas.
Choice A: No. The phrase mothers of infants in the breast-milk-fed group weighed significantly more on average than the mothers of babies in the formula-fed group is out of scope. The task of the question is to weaken the causal relationship between the consumption of breast milk and infants’ weights.
Choice B: No. The phrase Many of the infants in the formula-fed group…weighed more than the average weight of the breast-milk fed group is out of scope. Even if some individual infants in the formula-fed group weighed more than the average infant in the breast-milk-fed group, the study’s conclusions are based on the average rates rather than the weights of individuals. This does not weaken the causal relationship between the consumption of breast milk and infants’ weights.
Choice C: Correct. If The average weight of the infants in the breast-milk-fed group was significantly higher than that of the babies in the formula-fed group before the study began, there could be another cause for the weight difference between the two groups at the end of the study. This difference prior to the start of the study weakens the causal relationship between the consumption of breast milk and infants’ weights.
Choice D: No. The phrase a hormone found in breast milk has been linked to increased weight gain could strengthen the argument. If breast milk has been linked to weight gain in other studies, the conclusion of the passage would be strengthened. The task of the question is to weaken the argument in the passage.
Choice E: No. The phrase The average amounts of breast milk and formula consumed by the two groups…were approximately equal could strengthen the argument. If the amount of food eaten by the infants in both group is equal, this rules out an alternate explanation for the weight gain, which would strengthen the conclusion of the passage. The task of the question is to weaken the argument in the passage.
The correct answer is choice C.
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02 Nov 2018, 22:17
25%
(medium)
22%
(01:54)
wrong 
