#21 - In an experiment, some volunteers were assigned to

[tsolovey]

Getting the jump on question explanations here: Can someone please explain to me #21 in LR2? (The one about aerobics and weight lifting).

I can go through the other answers and eliminate them, but I also want to know exactly why E is actually the correct answer, or how it is an assumption required by the argument.

Thank you!

[Jon Denning]

Hi tsolovey - thanks for the question!

This is a really clever stimulus, in that it plays on a subtle but key shift in language/ideas from the premise (aerobics classes vs weight training) to the conclusion, which is no longer about aerobics classes, but rather about aerobic exercise. So when the conclusion states, causally, that aerobic exercise helps the body handle psychological stress based on the stress levels of the two groups, the connection required—the assumption, in other words—is that the group in the aerobics classes got more aerobic exercise than did the group taking weight-training classes!

That's one of the sneakiest Supported Assumption constructs I've seen in a while, where you need to recognize that taking aerobics classes doesn't necessarily guarantee more aerobic exercise than you'd get with weight training (both via the programs themselves, and outside of them), and then the answer closes that gap by ensuring that the aerobics classes group did indeed get more aerobic exercise.

Note too the power of the Assumption Negation Technique on (E): if the volunteers in the aerobics classes did NOT get more aerobic exercise, i.e. they did not get more of the thing the author believes is the cause of their lower-stress response, then arguing that extra aerobic exercise led to less stress doesn't make any sense and the conclusion falls apart! So as always that test really helps confirm that (E) is the winner here

Tricky idea, but hopefully that helps resolve it! If not please do let me know!

[lmasta0340]

I understand why E is correct, but I am having trouble eliminating answer choice B. At first glance, it seems like if those in the aerobics classes also lifted weights, it has the potential to be a confounding variable and impact the results of the study. Is there a way to eliminate this answer choice?

Thank you in advance!

[Christen Hammock]

Hey lmasta!

The conclusion of the argument is that aerobic exercise helps the body handle psychological stress—not that weight training doesn't! In that case, we would be still be left with two distinct groups to compare: an aerobic exercise group (with some weight training), and a weight training group (with no aerobic exercise). Answer Choice (E) provides the assumption that the author needs—that the weight training group was not getting as much or more aerobic exercise (including outside of class!) than the aerobic exercise group.

[ashpine17]

I’m going to go on a limb here and say B was the trap. Why exactly is this wrong? Wouldn’t it be problematic if people taking aerobics classes lifted weights as well? Maybe it was the weight lifting and not aerobics that caused this difference in performance?

[Adam Tyson]

Answer B is indeed a trap answer, ashpine17, but if it was not true, and the aerobics group also lifted weights, that would strengthen the argument by removing a possible alternate cause for the difference in the two groups. If they both lifted weights, but only one group did aerobics, then the weight lifting could not be responsible for the different stress levels. As it stands, an assumption of this argument is that weight lifting didn't negatively impact one's ability to handle psychological stress! So answer B is not a necessary assumption of the argument, and in fact it leaves a potential problem with the argument unresolved.

[silver2731]

Wow, as a non native English speaker I couldn't think of aerobic exercise as it was supposed to mean, I associated with exercises doing aerobics

[justlikemagic]

when i reviewed it on my own i understood why b was wrong but i still don't get why e is correct (i read the explanations above)

[Adam Tyson]

E is a necessary assumption of the argument, justlikemagic, because in order for aerobic exercise to have caused the different stress levels between the two groups, the two groups must have gotten different amounts of aerobic exercise. As Jon pointed out earlier in this thread, this answer becomes much clearer when you negate it: if the group in the aerobics class did not get more aerobic exercise than the group that lifted weights - if they had gotten the same amount of aerobic exercise, or even less - then the conclusion that aerobic exercise helped to remove stress would make no sense and have no support. That's what you want the Negation Technique to do with the correct answer; you want the negation to ruin the argument.

Looked at in a more abstract way, if you want to claim that a certain phenomenon caused a difference between two groups, then you must assume that the two groups exhibit a different level or rate of the occurrence of that phenomenon . If it turns out the two groups had the same rate of that phenomenon, then it could not have been the cause of any difference between them!

[Mmjd12]

(E) makes perfect sense to me now, but under timed conditions I chose wrongly for this question due to the syntax of words in the stimulus:

Premise: Some volunteers did aerobic exercise, some were assigned to weight lifting

Premise: After three months, each performed an arduous math calculation.

Conclusion: aerobic exercise helps the body handle psychological stress

I fell for (A), trying the Negation technique: Three months is not enough time for the body to fully benefit from aerobic exercise.

After reviewing it I realize this answer was a trap and actually has no effect on the argument because the stimulus does not claim the participants did aerobic exercise for 3 months. The amount of time each group spent working out is actually not specified. It only states that a period of 3 months had passed, then they did the math calculation.