- Fri Sep 23, 2016 6:07 pm
#28924
Hi, Zierra,
Good job getting this question right. This question asks you to identify a flaw in the reasoning, and as such your job is to work through the argument to arrive at your own prephrase, i.e. your own description of what you want to see in the credited response.
Proceeding from the stimulus, you should identify the conclusion, the premises offered in support, and in this case give an accurate description of the problem here. For problems such as this, your process might be as simple as asking yourself whether you concur with the author's reasoning. Can you envision any alternate possibilities that are consistent with the facts given?
For instance, I might imagine that there are actually so many different kinds of plants here because the soil is itself very fertile, not because of the plants.
Then turn this description into an abstract prephrase, preferably one that corresponds to one of the common flaws you have studied. In this case something like:
"The author mistakenly concludes that one thing (lots of plants) caused another thing (prairie ability to support life) when the cause could be reversed."
I know that you understand this, but it is essential to your success that you get the process right. Here it appears as though you might be working backwards from the answer choices. Sometimes you'll get the right answer anyways, but you will often get caught in an attractive trap, as you almost did here.
There are two ways you can know D is incorrect:
1) This answer choice describes a survey or sample flaw, which bears little resemblance to the reasoning here.
2) The general conclusion is in fact based on representative data, evidently enough to observe a direct correlation between number of plant species and plant health in different prairies.
To answer your last question, no you should not disregard an answer choice that refers to unrepresentative data based solely on the fact that a number is not mentioned. In fact, you will likely observe that there are many unrepresentative sample flaws that mention no precise numbers. c.f. PrepTest 16, LR Section 3, Problem 11 for an example.