PrepTest 118, Section 1, Question 11
The average cost of groceries will rise again(14 more words not shown)
The flawed reasoning in the(13 more words not shown)
- AThe price of(21 more words not shown)
- BEither the government(26 more words not shown)
- CThe average amount(29 more words not shown)
- DSince sugar is(41 more words not shown)
- EReal estate prices(37 more words not shown)
Reading the argument
Maybe butter and eggs will get cheaper.
Let's accept the premise that average grocery costs will rise next month. The argument doesn't establish that every grocery item will rise with that average. Meat and vegetables could become expensive enough to push the average up while butter and eggs stay the same or fall in price.
We're asked to find the same flawed reasoning elsewhere. The move is from a broad group's overall result to a claim about particular members, without showing which members account for that result. As another illustration, imagine the best hockey team in a tournament. It doesn't follow that every player on that team is better than every player on every other team. The group's result doesn't settle each member's result.
What we’re looking for
For a close match here, look for an increase in an overall average being used to establish an increase in a narrower part. The subject can change completely. What matters is whether the narrower claim actually follows.
Working the answers
- A
This keeps talking about gasoline. The move is from repeated increases in the past to another increase in the future. The original instead gives us next month's overall grocery increase and then narrows to butter and eggs. Predicting a later trend isn't the same as transferring a broad result to a particular part.
- B
This starts with two alternatives, then treats one as unlikely and concludes the other will happen. Being unlikely isn't being ruled out, so there is room to challenge that move. But it isn't our move from an average for a broad group to a claim about a subgroup.
- CCorrect
When I first see increased television viewing, I might expect the answer to narrow to one kind of program, such as soap operas. Instead, it narrows the people being measured. That's another way to make the same mistake.
People under twenty correspond to groceries as a whole. Fourth graders correspond to butter and eggs, a smaller group within the broader category. Teenagers could be watching much more television while fourth graders watch less. The overall average could rise without the particular group's amount rising, just as grocery costs could rise without butter and eggs becoming more expensive.
- D
This explicitly supplies the connection between the two prices: ice cream's price increases whenever sugar's price increases. With that rule given, the predicted sugar increase supports the predicted ice-cream increase. Mentioning food and next month doesn't create a match. The original never gives a rule that butter and eggs rise whenever the grocery average rises.
- E
This also supplies a rule connecting the change described in the premise with the predicted result. The specified population decline brings lower real estate prices, and that population is expected to decline. We might question that rule outside the problem, but accepting it here lets the conclusion follow. There is no unsupported move from a group average to one part.
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