Logical reasoning PrepTest 146 · Section 3 · Question 25

Incorrect. The conclusion here doesn't compare the relative size of the 20th century and 19th century art owned by the museum, and that comparison would need to be drawn for this answer to be parallel to the stimulus.

Incorrect. This answer reverses the stimulus—the premise is about what "more" people support, and the conclusion is what "most" people think.

Incorrect. This argument has a "most" premise and a "more" conclusion, but it's actually valid since the groups are compared to each other. If most trees are local, then there must be more local trees than other trees. In not switching between groups in the premise here, the argument avoids the flaw from the stimulus.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Flawed Parallel Reasoning

Stimulus Summary:
Sociology major-most-Intro to Social Psych
Psych major-most-not Intro to Social Psych
Therefore: More sociology majors in the class than psych majors

Answer Anticipation:
As soon as we see that the argument is providing us with quantifier statements ("most"), we should start to think about a quantifier/overlapping set flaw. Looking at the two quantified statements, however, there are no shared terms. The closest is that discussion of who's in the Intro to Social Psych classes, but one of our premises says that a subset of people are in the class and the other states that a separate subset isn't in the class. Since we can't take contrapositives of most statements, there's no inference that can be drawn by combining them, and so almost any conclusion will be invalid.

Reading the actual conclusion, we see that it heads in a different direction than we may have thought! It doesn't try to combine the two quantified statements—instead, it tries to compare the size of two groups based on proportions of those groups. In other words, it jumps from premises about percentages ("most" being over 50%) to a conclusion about numbers (there are "more" of one group in a class than another. That's problematic because we don't know the overall group sizes.

For example, if there are 10 sociology majors but 200 psych majors, then 10% of psych majors in the class would amount to double the number of total sociology majors.

Arguments can't jump from percentages to numbers, and this one does, so let's find an answer that makes a similar jump.

Answer Explanation:
This answer jumps from premises about "most" elements of one group having a characteristic that "most" of another don't, and drawing a conclusion about the relative sizes of those groups, so it's looking good:
Valley Food veggies → Organic
Jumbo veggies → not Organic
Therefore: More organic veggies are at Valley than Jumbo
That matches up, so we have our answer.

Key Takeaway:
Usually, arguments featuring quantified statements are flawed because they try to draw inferences about overlapping sets that aren't established as necessarily overlapping. However, another common flaw is in jumping from these statements to discussing the relative size of different groups. Quantifiers are percentages—they don't speak to numbers unless you know the group size—and so using them to support a conclusion about numbers (even relative size of different groups) is flawed.

Incorrect. This argument features a term shift in the conclusion—from photos on the website to actual properties for sale. In order to track with the stimulus, the comparison in the conclusion has to relate directly to the terms raised in the premises, so this answer isn't parallel.