A consumer magazine surveyed people who had sought a psychologist's help with a personal problem. Support Of those responding who had received treatment for 6 months or less, 20 percent claimed that treatment "made things a lot better." Support Of those responding who had received longer treatment, 36 percent claimed that treatment "made things a lot better." Therefore, Conclusion psychological treatment lasting more than 6 months is more effective than shorter-term treatment.
The author hypothesizes that psychological treatment lasting more than 6 months is more effective than shorter-term treatment. The evidence? A magazine survey where a greater percentage of people reported being very satisfied after 6 or more months of treatment, compared to those who had less than 6 months of treatment.
In order to conlude that treatment lasting longer than 6 months is more effective, the author must assume that there are no significant differences between the groups other than length of treatment. These differences could be factors like the type of issue being treated, or the patients' personal level of affinity for therapy.
Which one of the following, if true, most seriously weakens the argument?
Of the respondents who had received treatment for longer than 6 months, 10 percent said that treatment made things worse.
This doesn't have a comparative aspect—we don’t know what percentage of the group who received short-term treatment responded the same way. So, it can't help us.
Answer is attractive because it seems to (but doesn't actually) contradict the premises or conclusion.
Patients who had received treatment for longer than 6 months were more likely to respond to the survey than were those who had received treatment for a shorter time.
This isn't helpful. Regardless of the total numbers, the author is only looking at percentages. We also don't know if the difference in sample size makes a difference.
Weaken Qs: Answers that try to introduce an alternate explanation, but fall short, or try to explain a different phenomenon.
Strengthen Qs: Answers that try to eliminate an alternate explanation, but fall short, or try to eliminate an explanation for a different phenomenon.
Patients who feel they are doing well in treatment tend to remain in treatment, while those who are doing poorly tend to quit earlier.
This points out a key difference between the two groups of patients, which offers an alternative explanation for the survey results. This alternative explanation weakens the argument.
Weaken: Introduce or suggest an alternate explanation for the target phenomenon.
Strengthen: Helps to eliminate an alternate explanation for the target phenomenon.
Patients who were dissatisfied with their treatment were more likely to feel a need to express their feelings about it and thus to return the survey.
As far as we know, this applies equally to the two groups. Like (A), without a comparative aspect, this doesn't affect the argument either way.
Weaken Qs: Answers that try to introduce an alternate explanation, but fall short, or try to explain a different phenomenon.
Strengthen Qs: Answers that try to eliminate an alternate explanation, but fall short, or try to eliminate an explanation for a different phenomenon.
Many psychologists encourage their patients to receive treatment for longer than 6 months.
This is irrelevant. Like (A) and (D), without a comparison between the two groups, this doesn't help us. We also don't know how many is "many" or how that affects patients' decisions.
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