Critical Reasoning: Evaluate
- May 5, 2017
- Posted by: gmatdudes
- Category: Uncategorized
Written by Matt Keay
“Evaluate” questions will always have an argument stimulus, containing either a conclusion or a plan and goal. The answer choices will usually be questions that you do not know the answer to. The question stem will ask you to decide which question would provide the answer that would be the most useful in evaluating the argument.
A good way to check whether an answer choice is correct is to think of two opposite answers to the question, a strategy we call the “Variation Test”. If the two answers have opposite effects on the validity of the conclusion, that answer choice is correct. For example, let’s assume the two possible answers to a question are “yes” and “no”. If you assume the answer is “yes”, what happens to the conclusion? Is it strengthened? Is it weakened? Is the answer irrelevant? What about if you assume the answer is “no”? If one answer strengthens while the other weakens, that is almost certainly the correct choice. If you find that both answers are irrelevant / have no effect on the conclusion, that choice is incorrect.
Below is an example of a possible stimulus for an evaluate question.
“A recent survey of 100 regular coffee drinkers and 100 people who never drink coffee has shown that the coffee drinkers on average visit their doctor far more often than the people who never drink coffee. Therefore, it can be concluded that drinking coffee regularly can have negative effects on your health.”
Below are some possible correct answers for this stimulus:
“Do the coffee drinkers who were surveyed book general checkups considerably more often than the people who never drink coffee?”
This choice could be correct, because the answer to this question could help us determine whether the conclusion about coffee can be drawn based on the results of the survey. If the answer to this question is “no”, then that means that the difference in frequency of visits may be due to specific illnesses or concerns of the coffee drinkers, which may support the conclusion. If the answer is “yes”, we can guess that this accounts for the apparent disparity between the frequencies of the appointments of the two groups, and as a result, the conclusion is unjustified.
“What proportion of doctor’s visits of the coffee drinkers are in relation to illnesses or concerns that could conceivably be caused by drinking coffee?”
The answer could also be correct, because if the answer is “most of them”, then we have reason to believe that the argument’s conclusion is correct. If the answer is “very few of them”, then we can conclude that the coffee drinkers are primarily visiting their doctors for illnesses that cannot possibly be caused by coffee (or caffeine), and as such the conclusion would be unjustified.
Incorrect answer choices for this stimulus would primarily be questions that are totally irrelevant and that would not help to evaluate the conclusion. They may include choices similar to the choices below.
“Are there other hot drinks, such as tea, that are known to negatively affect the health of regular drinkers?”
“Were any of the coffee drinkers who were surveyed trying to quit drinking coffee?”
“What is the average price of a 500 gram bag of coffee powder?”
The answer to each of these questions could not possibly help us determine whether the argument’s conclusion is likely to be correct. The answers would be totally irrelevant, so these choices would all be incorrect.
Now we have an example of an official GMAT Evaluate question.
Scientists propose placing seismic stations on the floor of the Pacific Ocean to warn threatened coastal communities on the northwestern coast of the United States of approaching tidal waves caused by earthquakes. Since forewarned communities could take steps to evacuate, many of the injuries and deaths that would otherwise occur could be avoided if the government would implement this proposal.
The answer to which of the following questions would be most important in determining whether implementing the proposal would be likely to achieve the desired result?”
A. When was the last time that the coastal communities were threatened by an approaching tidal wave?
B. How far below sea level would the stations be located?
C. Would there be enough time after receiving warning of an approaching tidal wave for communities to evacuate safely?
D. How soon after a tidal wave hits land is it safe for evacuees to return to their communities?
E. Can the stations be equipped to collect and relay information about phenomena other than tidal waves caused by earthquakes?
(A) is incorrect, because the amount of time that has passed since the last tidal wave is irrelevant. We only care about whether the plan will save lives, and the answer to this question would not help us to find this out.
(B) is incorrect, because the depth of the stations will presumably have no effect on the likelihood of the plan achieving its goal.
(C) is correct, because if there is time to evacuate, then we have a reason to believe that the plan will work. If there is no time to evacuate, then the plan will obviously not achieve the goal of preventing injuries and deaths.
(D) is incorrect, because it is only concerned with something that will happen after the time when the plan is supposed to work. What happens after people have already evacuated is irrelevant.
(E) is incorrect because phenomena other than tidal waves are irrelevant. This plan is only concerned with preventing injuries and deaths by warning people of tidal waves, so we do not care whether it can collect information about underwater volcanoes for example.