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Using observations about how spouses spoke to each other, a researcher correctly predicted 90 percent of the divorces that occurred among the 200 couples he studied. Clearly, therefore, the way spouses speak to each other is an important determinant of how their relationships turn out.
The answer to which of the following would be most useful for evaluating the above argument?
A. In what proportion of divorces among the studied couples did the researcher not predict a divorce?
B. Are there factors that have a greater impact on the longevity of a marriage than how much time, on average, spouses communicate with each other daily?
C. Were there any couples among the 200 studied by the researcher who spoke to each other well but got divorced?
D. In what proportion of the cases in which the studied couples did not get divorced did the researcher predict a divorce?
E. Did the researcher himself make the observations about how couples talked to each other?
Target Test Prep Official Explanation:The argument concludes that “the way spouses speak to each other is an important determinant of how their relationships turn out.”
That conclusion is based on the fact that “Using observations about how spouses spoke to each other, a researcher correctly predicted 90 percent of the divorces that occurred among the 200 couples he studied.”
To correctly answer the question, we need to find a choice the answer to which helps with evaluating the likelihood that the conclusion is correct.
(A) In what proportion of divorces among the studied couples did the scholar not predict a divorce?The answer to this question would not provide any information we don’t already have. After all, if, as the passage says, the researcher predicted 90 percent of the divorces, then we know that the researcher did not predict 10 percent of the divorces since 100 percent - 90 percent = 10 percent.
(B) Are there factors that have a greater impact on the longevity of a marriage than how much time, on average, spouses communicate with each other daily?The answer to this question is irrelevant. Regardless of whether other factors have a greater impact on the longevity of a marriage, it could be the case that the way spouses speak to each other is an important determinant of how their relationships turn out.
(C) Were there any couples among the 200 studied by the researcher who spoke to each other well but got divorced?Notice that, even if some couples spoke well to each other and got divorced, it still could be the case that the way spouses speak to each other is an important determinant of how their relationships turn out. The conclusion is not that speaking well solves all relationship problems. Also, “any” could be just one or two couples.
Also, the support for the conclusion is that the researcher predicted 90 percent of the divorces that occurred. So, we already know that 10 percent of the divorces were not predicted through observation of how the people spoke to each other. Thus, the answer to this question would not provide any useful new information.
(D) In what proportion of the cases in which the studied couples did not get divorced did the researcher predict a divorce?
Correct AnswerNotice that, if the answer to this question is “a large proportion,” then the support for the conclusion is weakened.. After all, in that case, it appears that the researcher simply predicted that most of the couples, both those who did get divorced and those who didn’t, would get divorced.
So, in that case, the fact that the researcher correctly predicted the divorces is meaningless. The researcher’s method didn’t really work. He just predicted that most people would get divorced, and his prediction seemed correct in the cases of people who did get divorced.
So, if the answer to this question is “a high proportion,” the fact that the researcher predicted the divorces doesn’t provide much support for the conclusion.
On the other hand, if the answer to this question is “a small proportion,” then the researcher’s method seems to work well, and the argument is strengthened.
Thus the answer to this question is helpful in evaluating the argument.
(E) Did the researcher himself make the observations about how couples talked to each other?The answer to this question is not helpful because the observations and predictions remain essentially the same regardless of whether the researcher himself made the observations.
Answer: D