Psychology researchers found that manual laborers who were tutored on

­Psychology researchers found that manual laborers who were tutored on the fitness value of their tasks experienced marked health improvements. Despite workload and levels of recreational exercise remaining constant, within four weeks of learning that their daily tasks provided good exercise, the participants lost an average of two pounds and achieved statistically meaningful reductions in body-fat percentage compared with an untutored group. The psychologists hypothesized that this improvement in fitness levels was a direct result of their heightened perception of themselves as fit.

The researchers have hypothesized the following:

this improvement in fitness levels was a direct result of their heightened perception of themselves as fit

The support for that conclusion the following:

manual laborers who were tutored on the fitness value of their tasks experienced marked health improvements ... the participants lost an average of two pounds and achieved statistically meaningful reductions in body-fat percentage compared with an untutored group

One key thing we need to notice as we read the passage is the following:

Despite workload and levels of recreational exercise remaining constant

This type of detail, information that variables were held constant or controlled for, seems to have become common in GMAT Critical Reasoning questions, and it can be the reason why an answer choice is not correct. So, we need to notice that type of detail in a passage.

Which of the following would it be most useful to determine in evaluating the hypothesis?

This is an evaluate question. So, the correct answer will be the one such that different answers to the question the choice presents will weaken or strengthen the case for the hypothesis.

(A) Whether people who believe themselves to be fit are likely to eat less than those who do not believe themselves to be fit

The hypothesis is the following:

this improvement in fitness levels was a direct result of their heightened perception of themselves as fit

So, a yes answer to the question presented by this choice weakens the case for the conclusion. After all, if "people who believe themselves to be fit are likely to eat less than those who do not believe themselves to be fit," then the reductions in weight and body fat percentage of the tutored participants may not have been a "direct" result of their heightened perception of themselves as fit. In that case, it could be that the reductions were indirect results of their perceptions and were actually directly caused by their eating less.

On the other hand, a no answer to this question strengthens the argument by serving to confirm that eating less is not the direct cause of the tutored participants' reductions in weight and body fat percentage and thus providing more reason to believe that the improvement was indeed a "direct" result of their heightened perception of themselves as fit.

Keep

(B) What percentage of the participants in the study believed themselves to be at least moderately fit before the study began

The hypothesis involves the participants' "heightened" perceptions of themselves as fit.

The tutoring would have caused the perceptions of themselves as fit to become heightened regardless of whether they "believed themselves to be at least moderately fit before the study began."

So, the answers to the question presented by this choice have no effect on the case for the hypothesis.

Eliminate.

(C) Whether frequently being ill tends to lead people to perceive themselves as not being fit

Since we have no reason to believe any of the partipants were ill, the answers to the question presented by this choice have no effect on the argument.

Eliminate.

(D) What percentage of the participants in the study continued after four weeks to lose weight and reduce their body-fat percentage

Regardless of what the participants did after four weeks, the comparison between what occurred with the different groups of participants during the four weeks supports the hypothesis.

If the pattern continued to occur after four weeks, we don't have any more reason to believe that the hypothesis is correct. After all, it would still be the same pattern, just longer. If the pattern did not continue after four weeks, the fact that it occurred during the four weeks still supports the hypothesis.

Eliminate.

(E) Whether the perception of oneself as fit causes one to enjoy, and thus participate more frequently in, recreational exercise

We could see this choice as similar to choice (A).

So, we might get the impression that a yes answer to the question presented by this choice weakens the case for the conclusion. After all, if "the perception of oneself as fit causes one to enjoy, and thus participate more frequently in, recreational exercise," then maybe the tutored participants' reductions in weight and body fat percentage were not a "direct" result of their heightened perception of themselves as fit. In that case, it could appear that the reductions were indirect results of their perceptions and were actually directly caused by recreational exercise.

Similary, we could get the impression that a no answer to this question strengthens the argument by serving to confirm that recreational exercise is not the direct cause of the reductions in weight and body fat percentage of.

So, how does this question work if two choices seem about the same?

If you didn't already notice why this choice doesn't work, your move is to bounce back to the passage and see what's going on. What you can see in rereading the passage is that it says that the tutored laborers experienced marked health improvements "Despite workload and levels of recreational exercise remaining constant."

We see that the passage confirms that the tutored laborers did not "participate more frequently in ... recreational exercise" because exercise that remained "constant" did not become more frequent.

So, the answer to the question presented by this choice makes no difference because, regardless of what the answer is, the study participants did not exercise more frequently.

Eliminate.

Correct answer: A­