Logical reasoning PrepTest 151 · Section 2 · Question 18

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:
Termites have been found at every fairy circle, so termite burrowing must cause the fairy circles.

Answer Anticipation:
Classic correlation vs. causation flaw. When you come across a Strengthen question that commits this error in reasoning, expect the answer to:

(1) Rule out an alternative cause;
(2) Find more examples of the supposed cause and effect correlating;
(3) Find an example where the supposed cause doesn't exist, and the effect isn't seen; or
(4) Explain how the cause would lead to the effect.

Answer Explanation:
This answer both shows the cause and effect going together (burrowing; damage at the root) and explaining how the termites cause the fairy circles.

Key Takeaway:
While less common, an answer that explains how a hypothesized cause could lead to an effect does strengthen that relationship.

Incorrect. This answer might seem to rule out an alternative cause—drought isn't causing the grass to die. However, this answer doesn't clearly state what type of vegetation existed inside the fairy circle, so it's impossible to know how it affects the hypothesis.

Incorrect. Is higher water content good or bad for vegetation in the Namib Desert? Without knowing that, we can't tell if this answer is bringing up a potential cause of the fairy circle (excessive water) or ruling one out (not enough water).

Incorrect. This answer supports a hypothesis that fairy circles are caused by something that is local. Does that apply to termites? We're not told—maybe they tend to fly great distances between creating colonies.

Incorrect. First, this statement is a weaker correlation than that given in the stimulus—here, it's "often;" there, it's "every." Second, if anything, this suggests an alternative cause—the animals digging for sand termites caused the fairy circle.