This type of critical reasoning question, often called an evaluate question, involves answer choices that will affect whether the conclusion. Evaluation questions can be detected by looking for the key words evaluate, most useful to know, most useful to determine, or just finding that the answer choices are all questions or all start with the word whether.
The first step with this problem is to identify the conclusion. It is: switching to the modified seed would be unlikely to benefit most cotton farmers economically.
Why? Because the modified seed costs more than ordinary seed without producing yields of higher market value and because the amount of insecticide needed per acre to control insect pests was only slightly lower for those who tried the modified seed than for those who did not.
In most cases, evaluate questions can be resolved using the variance test. This test involves providing opposite answers to the choices to see what effect this variance has on the conclusion. Let's start with (A).
Yes, farmers who tried the modified cotton seed has tried growing other crops from genetically modified seed. Does that answer strengthen the argument? No. Does it weaken it? No. What if I switch the answer to no? Will that weaken or strengthen? No. This is merely irrelevant information that does not impact the conclusion.
(B) Yes, the insecticides typically used on ordinary cotton tend to be more expensive than insecticides typically used on other crops. Does that strengthen? No. Does it weaken? No. What if I switch the answer to no? Again, we see that it will have no effect. We are not interested in comparing the cost of insecticide for cotton to the cost of insecticide for other plants.
Now let's try answer choice (D), the credited response. Yes, the farmers who have tried the modified seed plants as many acres of cotton, on average, as farmers using the ordinary seed did. Does that strengthen the argument? No. The argument specifically says "the amount of insecticide needed per acre...was only slightly lower." So the number of acres is irrelevant. Regardless of whether the farmers planted 100 acres or 1000, the seed costs more, doesn't produce a greater yield, and the amount of insecticide needed per acre was only slightly lower.
So what gives? Why doesn't this work with the credited response? Well, the answer is simple: This question isn't the real question! It's been inexpertly modified. Let's look at the real, official question:
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Scientists have modified feed corn genetically, increasing its resistance to insect pests. Farmers who tried out the genetically modified corn last season applied less insecticide to their corn fields and still got yields comparable to those they would have gotten with ordinary corn. Ordinary corn seed, however, costs less, and what these farmers saved on insecticide rarely exceeded their extra costs for seed. Therefore, for most feed-corn farmers, switching to genetically modified seed would be unlikely to increase profits.
Which of the following would it be most useful to know in order to evaluate the argument?
(A) Whether there are insect pests that sometimes reduce feed-corn yields, but against which commonly used insecticides and the genetic modification are equally ineffective
(B) Whether the price that farmers receive for feed corn has remained steady over the past few years
(C) Whether the insecticides typically used on feed corn tend to be more expensive than insecticides typically used on other crops
(D) Whether most of the farmers who tried the genetically modified corn last season applied more insecticide than was actually necessary
(E) Whether, for most farmers who plant feed corn, it is their most profitable crop
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Conclusion: for most feed-corn farmers, switching to genetically modified seed would be unlikely to increase profits.
Why? Because Ordinary corn seed costs less, and what these farmers saved on insecticide rarely exceeded their extra costs for seed and because farmers who tried out the genetically modified corn last season applied less insecticide to their corn fields and still got yields comparable to those they would have gotten with ordinary corn.
Now let's try the variance test on (D), the credited response.
Yes, most of the farmers who tried the genetically modified corn last season applied more insecticide than was actually necessary. Does that weaken the conclusion? Absolutely! If farmers applied more insecticide than was necessary, that means that they could have used less insecticide, spent less money, and potentially improved their profits.
Elias Latour
Verbal Specialist @ ApexGMAT
blog.apexgmat.com
+1 (646) 736-7622
