Logical reasoning PrepTest 151 · Section 3 · Question 21

Incorrect. It's not necessary for the argument that the aerobic group fully benefited from the exercise, just that they got at least some benefit from it.

Incorrect. It doesn't matter who lifted weights, since the conclusion is about aerobic activity. We know that group did some aerobics, so even if they lifted, the fact that the aerobic + weights group had less stress than the weights group would still suggest aerobic activity was a factor in the stress reduction.

Incorrect. The relevant comparison is total aerobic activity between the two groups, not how much more exercise the aerobics group got than before the study started.

Incorrect. Psychological stress levels matter, not difficulty. While there may be some relationship between stress and difficulty, it isn't definitively established in the argument, so we can't need to assume a connection for the argument to function.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
Two groups were formed. One was sent to aerobics; the other weight training. 3 months later, it was less stressful for the aerobics class to do math than the weight training class, so aerobics must help with mental stress.

Answer Anticipation:
The one group definitely did aerobics. However, we don't know much about the other group's level of aerobic activity, other than they weren't forced to do it as a part of the study. In order to reach the conclusion, it must be established that the former group definitely engaged in more aerobic activity than the latter.

Answer Explanation:
This answer brings up the relevant comparison. In order to reach the conclusion that aerobic activity led to less psychological stress, it must be established that the group forced to do aerobic activity had more of it than the other group. If the former group did 30 minutes of forced aerobic activity, but the latter group all did an hour of aerobic activity after their 30 minutes of forced weight lifting, the conclusion falls apart.

Key Takeaway:
When two groups are compared, make sure that you learn all relevant information, and don't assume anything is true by omission. Here, the argument states that each group participated in an activity, but it doesn't state that they didn't participate in others. The writers of the exam are hoping you'll write that information in yourself and get this question wrong.