PrepTest 123, Section 3, Question 15
A consumer magazine surveyed people who had sought(61 more words not shown)
Which one of the following,(7 more words not shown)
- AOf the respondents(17 more words not shown)
- BPatients who had(26 more words not shown)
- CPatients who feel(21 more words not shown)
- DPatients who were(23 more words not shown)
- EMany psychologists encourage(10 more words not shown)
Reading the argument
What happens to the people who try treatment, decide it isn't helping, and stop going?
I'd want to know before crediting the extra months with the better results. We have 20 percent reporting that things got a lot better after six months or less, compared with 36 percent among people treated longer. That could mean more time helps. But it could also mean the people who aren't doing well leave before they ever become part of the longer-treatment group.
Imagine that treatment already feels helpful after a few months. You have a reason to keep going. Now imagine paying for appointments month after month without feeling any better. You might quit. If those are the decisions people make, the longer-treatment group will contain a greater share of people who were happy with their results to begin with. The extra months don't have to create the difference.
Put numbers on it. Suppose 1,000 people start, and 200 report feeling a lot better. That's 20 percent. Now suppose 450 people who aren't reporting that improvement leave, while the 200 who feel better stay. We have the same 200 positive reports among 550 remaining people: about 36 percent. Nobody new had to improve for the percentage to rise.
What we’re looking for
These are hypothetical numbers, not facts about the survey. They show why the comparison doesn't settle the cause. We also don't know whether the groups had similar personal problems, and we're relying on what people say about their improvement. But the quitting possibility gives us a particularly direct way to weaken the argument: show that doing well makes people more likely to stay in treatment.
Working the answers
- A
What percentage of the shorter-treatment group said things got worse? Without that comparison, we can't tell whether 10 percent makes longer treatment look better or worse. If 30 percent of the shorter-treatment group reported harm, this new measure would favor longer treatment too. A gives us information about one group without establishing the unfavorable comparison we need.
- B
This says the longer-treatment group is more likely to send in a response. It doesn't say that the responses from that group are more likely to be positive because of who responds.
We can compare percentages even if we hear from different numbers of people in the two groups. For a response pattern to undermine this particular comparison, we'd want to know that it distorts the groups differently with respect to how well treatment worked. B gives us a difference in overall response rates, but not that connection.
- CCorrect
People who feel they're doing poorly tend to quit early; people who feel they're doing well tend to stay. That's exactly the pattern that could make longer treatment look more effective without the additional time producing the improvement.
The longer-treatment group has been shaped by people's decisions to continue. Return to the numbers: removing people without positive reports can turn the same 200 positive reports into a much larger percentage. C doesn't prove that extra treatment has no benefit. It gives us a competing explanation for the difference the argument treats as evidence of that benefit.
- D
Dissatisfied patients being more likely to respond could make the survey look negative overall. But why would that produce 20 percent positive responses in one duration group and 36 percent in the other? D doesn't say that this pattern affects one group more than the other. It raises a general concern about the survey without explaining away the specific comparison.
- E
Encouraging longer treatment doesn't establish whether longer treatment works better. Perhaps psychologists make this recommendation because it helps; perhaps the recommendation is mistaken. E gives us the advice without evidence about its effectiveness, so it doesn't undermine the argument's comparison.
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