The author's conclusion is that "at least one type of memory {i.e. the type required to remember to make a phone call at a certain time} does not suffer as a person ages. How does the author arrive at that conclusion?
- A recent study compared Group A (persons sixty-five to seventy-five years old) to Group B (college students).
- Each member of the two groups was asked to call a certain phone number at a certain time.
- "The time when each call was initiated was recorded electronically", allowing the scientists conducting the study to see whether the group members made the calls at the requested times.
- "Group A proved far better at remembering to make a telephone call precisely at a specified time than did Group B." In other words, members of Group A did a better job of making the phone calls at the specific times requested.
- How much better did Group A do compared to Group B? "There were 14 lapses in Group B but only one lapse in Group A."
Thus, it seems as though the members of Group A were better able to remember to make a phone call at a certain time. But what information would be useful in establishing whether that line of reasoning is accurate? Any statement that IS useful should be eliminated because we are looking for the statement that would be the LEAST useful:
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(A) There was the same number of people in each group.
Yes, this would be useful to know. What if Group B had 1000 members but Group A only had 10? In that case, the difference in the number of lapses could be contributed to group size, not to a difference in memory between the two groups. Thus, (A) should be eliminated.
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(B) The same group of researchers answered the calls made by callers in both study groups.
All we need to know is whether the group members made their calls at the specific requested times. "The time when each call was initiated was recorded electronically," so it doesn't matter who answered the calls. (B) does NOT help us evaluate the argument or conclusion, so let's hang on to it.
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(C) Among the college students there were no persons more than forty years old.
Remember, the conclusion is that "at least one type of memory does not suffer as a person ages." This conclusion is based on evidence comparing a group of college students to a group of persons sixty-five to seventy-five years old. This argument ASSUMES that the college students were much younger, but what if that was not the case? What if most of the college students participating in the study were actually older adults or even senior citizens over sixty-five years old? That would certainly harm the author's argument. Statement (C) WOULD be useful in evaluating the conclusion, so it should be eliminated.
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(D) Both groups had unrestricted access to telephones for making the required calls.
What if the college students (Group B) did not have unrestricted access to telephones while the members of Group A did have such access? In that case, the difference in the number of lapses could be contributed to telephone access, not to a difference in memory between the two groups. Thus, (D) would be helpful and should be eliminated.
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(E) The members of the two groups received their instructions approximately the same amount of time before they were to make their telephone calls.
Again, this would provide an alternate reason to explain the difference in the number of lapses. If the college students in Group B were only give a very short amount of time and the members of Group A were given a lot of time, that might have given the members of Group A more time to prepare and make sure they would be ready to make the calls at the specified times. (E) would be helpful and should be eliminated.
Choice (B) is the best answer.
I hope that helps clear up some of the confusion!