Logical reasoning PrepTest 144 · Section 3 · Question 15

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Study Ð Volunteers were split into 5 groups that each compared Sparkle Cola to a different soda
Results Ð Most volunteers preferred Sparkle Cola to the competitor
Conclusion Ð Sparkle Cola gets the best response of all colas tested

Answer Anticipation:
This stimulus starts by establishing that the argument is based on a study, and whenever there's a study (or survey, or poll), we should start by considering a sampling flaw, and a correlation/causation flaw.

Here, the study is noted as being carefully controlled, and the volunteers were divided evenly into groups. There's no indication that the sample wasn't large enough, or the volunteers were unrepresentative in some key way, or that the assignments weren't random. If an answer establishes that to be true, it could be correct, but we shouldn't expect a sampling flaw.

For the correlation/causation flaw, the conclusion of the argument is that something is preferred, not that something causes another, so there's no correlation/causation flaw. We'll have to look somewhere else for the flaw here!

Since the results of the study are the key to the conclusion, we should start by looking there. It establishes that the majority of the volunteers preferred Sparkle Cola to the competitor they tasted. However, the volunteers didn't each test all of the competitors—they were divided into five groups that each tested one. If the majority that preferred Sparkle Cola weren't evenly distributed, then the majority could prefer Sparkle Cola despite one competitor actually beating it out in the group.

Think of it this way—let's say there were 100 people in each group. In 4 of the groups, 100% of the people preferred Sparkle Cola to the competitor. In the remaining group, 100% of the people preferred the competitor. If that's the case, the majority of the volunteers would have preferred Sparkle, but there would be a soda out there that was preferred over it.

Short version? The argument shifts from discussing groups to discussing individuals, assuming that what's true of one is also true of the other.

Answer Explanation:
This answer highlights the shift from discussing what is true of the volunteers as a group of individuals in the premise to a conclusion about what is true of each individual group.

Key Takeaway:
Be sure to note the scope of the argument as defined by the conclusion. Many answers will treat the conclusion as if it had a wider scope than it did, and noting that can allow you to quickly eliminate those answers (see (C) and (E)).

Incorrect. The argument is about the consumer response to the Cola, not whether they'd purchase it.

Incorrect. The conclusion limits itself to discussing the "competing colas tested," so other colas are out of scope.

Incorrect. This aligns with the argument. If it stated that the other colas might be preferred for this reason, then it could be correct.

Incorrect. The conclusion limits itself to comparing Sparkle to the competing colas tested, so beverages other than colas are out of scope.