September 2018 LSAT Section 3 Question 21

In an experiment, some volunteers were assigned to take aerobics classes and others to take weight-training classes. ...

Chidera on January 21, 2020

Why not D?

For this question, I still have a hard time understanding why D is not the correct choice. I still don't understand from the last explanation how E is the correct choice since nothing is stated in the paragraph or question about the amount of time spent in aerobic exercise or weight training.

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Annie on January 21, 2020

Hi @chidera,

This question asks you to find the assumption buried in the argument. When looking at this type of question, I always like to begin by breaking down the argument into its component parts:

Premise: In an experiment, some volunteers took aerobics classes and others weight training classes.
Premise: After 3 months, the aerobics takers had less measurable stress after doing a math problem then the weight trainers did.
Premise: ???
Conclusion: This supports that aerobics helps the body handle psychological stress.

Answer (D) is incorrect because it is actually the opposite of what the argument is saying. If the aerobic class takers found the question less difficult, then the argument could not point to the workout class as necessarily the cause of their having less stress. This answer choice is adding in another possible factor (aka that the aerobics takers just like math more, or are better at it) which could cause the result discussed, so it actually doesn't support the conclusion.

Answer (E) on the other hand eliminates a possible competing factor in the argument. In order for the conclusion to hold, the aerobics group must have gotten more aerobic exercise on the whole then the weight group. If it happened that the weight group was also running, then the conclusion wouldn't hold because they'd actually be getting more aerobic exercise. You can double check this answer by negating it. In that case, the volunteers assigned to the weight group would get more aerobic exercise overall than the aerobic group. If that were true, the conclusion would fail, making this the right answer.

Devin on September 15 at 08:30PM

So what youre saying is if B was flipped and negated essentially we would have the correct answer? Did I understand that right?

Emil on September 18 at 08:31PM

I think so- if it said that the weightlifters did not also do aerobics I think B would be correct.