PrepTest 144, Section 4, Question 13
Government statistics show that the real (adjusted for(36 more words not shown)
The reasoning in the argument(11 more words not shown)
- Aambiguously uses the(6 more words not shown)
- Bfails to take(10 more words not shown)
- Coverlooks the possibility(7 more words not shown)
- Dfails to consider(15 more words not shown)
- Epresumes, without providing(14 more words not shown)
Reading the argument
Average family income rose. Did this family's income rise?
The Andersens could be moving in the opposite direction. Suppose the family's highest earner lost a well-paying job and took one with lower pay. The family's income could have fallen even while the average rose. Being at the average now doesn't tell us where the family started.
Put numbers on it. Imagine the average rose from $50,000 to $60,000, while the Andersens' income fell from $100,000 to $60,000. They are exactly average this year, just as the passage says. Yet their income decreased. Treat all those figures as adjusted for inflation, so inflation doesn't explain away the example.
What we’re looking for
For the flaw question, look for the missing information about the family's past. A trend in the overall average doesn't establish the same trend for each individual family.
Working the answers
- A
“Average” refers to the same income benchmark in both uses. The argument doesn't shift from one meaning of the word to another. The mistake is assuming that a family at today's average must have followed the average's recent path.
- B
The passage expressly defines real income as adjusted for inflation and concludes that the family's real income rose. Inflation has already been accounted for. The example in the prelude still defeats the inference even with that adjustment.
- C
Most families' incomes could be below the average. For a simple illustration, the average of 1, 1, and 10 is 4, and two of those three numbers are below 4. But this possibility doesn't identify the argument's mistake. We are already told that this family's current income is average; the missing fact is its past income.
- DCorrect
The family could previously have earned more than the average and then fallen to today's average. The $100,000-to-$60,000 example shows how that could happen while the overall average rises. Being above average in the past wouldn't by itself prove the family lost income. It makes clear why we cannot assume the increase claimed in the conclusion.
- E
We can grant the government perfectly accurate figures and the argument still fails. Those figures describe the average, not the Andersens' earlier income. The problem isn't a need to assume that government data collection never contains an error.
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