PrepTest 146, Section 3, Question 25
At Morris University this semester, most of the(30 more words not shown)
The flawed pattern of reasoning(15 more words not shown)
- AMost of the(43 more words not shown)
- BIn an opinion(48 more words not shown)
- CIn the San(32 more words not shown)
- DMost of the(35 more words not shown)
- EThe Acme Realty(32 more words not shown)
Reading the argument
What if the psychology department is much bigger? A majority of a small group can easily be outnumbered by a minority of a large one.
Suppose there are 10 sociology majors and 6 take the class. There are also 100 psychology majors, of whom 25 take it. Most sociology majors are enrolled, and most psychology majors are not. Yet the class has 25 psychology majors and only 6 sociology majors. Both premises hold while the conclusion fails.
What we’re looking for
The parallel argument needs that same jump: most of one group has a particular feature, most of another group lacks it, so the first group supposedly contributes more things with that feature. We can't compare those numbers without knowing the sizes of the groups.
Working the answers
- A
There is a promising beginning here. The two groups are displayed paintings and owned paintings; the shared feature is being from the twentieth century. Most displayed paintings have that feature, while most owned paintings don't—nineteenth-century paintings aren't twentieth-century paintings.
But the conclusion changes the task. It says the museum owns few of the twentieth-century paintings it displays. That's a claim about overlap between what is owned and what is displayed. To match the original, it would need to compare the number of twentieth-century paintings displayed with the number of twentieth-century paintings owned. A doesn't draw that conclusion.
- B
This compares support for two policies within one poll. More people favoring roads than parks doesn't mean that most residents favor roads, and it doesn't mean road supporters oppose parks. Someone could support both. The error concerns the size and overlap of preference groups within the same surveyed population, rather than comparing two groups' contributions based on most versus not most.
- C
This moves from the trees in an arboretum to the trees in the surrounding area. The arboretum could deliberately contain an unusual selection of trees. That's a problem with treating one location as representative of a larger area, not the original's failure to account for two groups having different total sizes.
- DCorrect
Valley Food and Jumbo play the roles of the sociology and psychology groups. Being organic plays the role of taking the class. Most Valley vegetables are organic; most Jumbo vegetables aren't. The conclusion then compares the actual numbers of organic vegetables.
But a small co-op could have mostly organic vegetables while a huge supermarket has many more organic vegetables despite their being a minority of its stock. Just like the 6 sociology students and 25 psychology students, the larger percentage can produce the smaller number.
- E
The premises fit closely: houses and condominiums are the two groups, and having a website photo is the shared feature. Most houses have photos, while fewer than half the condos do. But the conclusion compares all houses for sale with all condos for sale. The original compares only the majors enrolled in the class. An exact match here would conclude that there are more photographed houses than photographed condos. E instead draws a conclusion about the total populations.
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