Self-study
At Morris University this semester, most of the sociology majors are taking Introduction to Social Psychology, but most of the psychology majors are not. Hence, there must be more sociology majors than psychology majors enrolled in the class.
25.
The flawed pattern of reasoning in the argument above is most similar to that in which one of the following?
a
Most of the paintings on display at the Metro Art Museum are from the twentieth century, but most of the paintings the Metro Art Museum owns are from the nineteenth century. It follows that the museum owns few if any of the twentieth-century paintings it displays.
(A) is talking about 4 categories of paintings — 20th century paintings on display, 20th century paintings owned, 19th century paintings on display, and 19th century paintings owned. The stimulus is only talking about 2 categories — sociology students in Social Psychology and psychology students in Social Psychology.
b
In an opinion poll of Silver Falls residents, more said they were in favor of increased spending on roads than said they were in favor of increased spending on parks. So most Silver Falls residents must be in favor of spending more on roads but opposed to spending more on parks.
(B) makes a different mistake — it has the relative vs absolute flaw. It assumes that a majority support spending more on roads and a majority oppose spending more on parks. But it could be that 95% want to spend more on roads, and 90% want to spend more on parks. (B) confuses relative (which has more support) with absolute (which have at least 50% support).
c
In the San Felipe city arboretum, most of the trees are of local rather than exotic species. Therefore, in the San Felipe area, there must be more trees of local species than of exotic species.
(C) has a different flaw — confusing part and whole. It assumes that what is true of the aboretum is true of the entire San Felipe area.
d
Most of the vegetables available at the Valley Food Co-op are organic, but most of the vegetables available at the Jumbo Supermarket are not. Thus, more organic vegetables are available at Valley Food than are available at Jumbo.
(D) states that most of A (vegetables at Valley Food Co-op) are organic, but that most of B (vegetables at Jumbo Supermarket) are not. Thus, the author concludes that the number of organic vegetables among A is greater than the number among B. This is the same reasoning as in the stimulus, and has the same flaw: both confuse percentages with amounts. Maybe the Jumbo Supermarket is far bigger, and thus has more organic vegetables.
e
The Acme Realty website has photos of most of the houses, but of fewer than half of the condominiums, that Acme is offering for sale. So Acme must have more houses than condominiums for sale.
(E) states that most of A (houses) have photos on the website, but that most of B (condos) do not. For (E) to be parallel, the next sentence should say “thus, there are more photos of houses than of condos on the website”. Instead, (E) makes an unrelated conclusion about the amount that are for sale, as opposed to the amount that have pictures.