PrepTest 103, Section 3, Question 19
Over the past 20 years, skiing has become(82 more words not shown)
The reasoning in the argument(11 more words not shown)
- AIt fails to(15 more words not shown)
- BIt infers disparate(6 more words not shown)
- CIt ignores the(13 more words not shown)
- DIt assumes that(18 more words not shown)
- EIt proceeds as(20 more words not shown)
Reading the argument
Did better equipment cause the injury decline, or could better instruction or safer slopes have helped? That's what I first wonder as I read the opening.
But the argument then takes a different turn. The author claims that injuries haven't declined in every category, pointing to knee injuries rising from 11 percent to 16 percent of all injuries. Now we need to compare a share of the total with an actual number.
The total number of injuries has fallen by half. Suppose it was 100 before and is 50 now. Eleven percent of 100 is eleven knee injuries. Sixteen percent of 50 is eight knee injuries. The share rose, but the number fell from eleven to eight.
So a bigger slice of a smaller total can still mean fewer injuries. In fact, the given percentages and the halved total show a drop in knee injuries, rather than establishing the absence of one.
What we’re looking for
For the flaw question, that's our target. Whatever caused skiing to become safer, the author's numerical comparison doesn't support the claim about which injury counts declined. Look for treating an increased percentage as if it ruled out a decreased number.
Working the answers
- A
The passage needn't exclude other injuries, such as head injuries, for this mistake to occur. It already gives us the total injury decline and the knee-injury percentages. Those are enough to test the knee-injury claim. Whether other categories exist doesn't repair the move from a larger share to no decrease in number.
- B
One cause can have different effects on different kinds of injury. Better equipment might protect one part of the body more than another, so differing effects aren't automatically a flaw. More importantly, the challenged conclusion concerns the number of injuries in particular categories. The percentage-to-number mistake is what prevents this evidence from establishing that conclusion.
- C
A change in the number of skiers would matter to injury risk per skier. But the conclusion here concerns injury counts, and the passage directly gives the change in the total count. Adding more skiers doesn't make 16 percent of the new, halved total exceed 11 percent of the old total. C doesn't identify the numerical error.
- DCorrect
The argument treats knee injuries' larger proportion as if their number couldn't have decreased. Our example shows both can happen together: eleven of 100 injuries becomes eight of fifty. Knee injuries fall in number but rise as a share because the total falls even faster. D identifies the precise confusion, not merely a general concern about statistics.
- E
If every injury category declined by more than 50 percent, the overall total would also have to decline by more than 50 percent. But the author doesn't claim that every category has a greater decline than the total. The author cites a 90-percent drop for certain injuries and wrongly treats knees as a category without a decline. That isn't the all-categories claim E describes.
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