June 2007 PrepTest, Section 3, Question 15
A consumer magazine surveyed people who had sought a psychologist's help with a personal problem. Of those responding who had received treatment for 6 months or less, 20 percent claimed that treatment "made things a lot better." Of those responding who had received longer treatment, 36 percent claimed that treatment "made things a lot better." Therefore, psychological treatment lasting more than 6 months is more effective than shorter-term treatment.
A consumer magazine surveyed people who had sought a psychologist's help with a personal problem. Of those responding who had received treatment for 6 months or less, 20 percent claimed that treatment "made things a lot better." Of those responding who had received longer treatment, 36 percent claimed that treatment "made things a lot better." Therefore, psychological treatment lasting more than 6 months is more effective than shorter-term treatment.
A consumer magazine surveyed people who had sought a psychologist's help with a personal problem. Of those responding who had received treatment for 6 months or less, 20 percent claimed that treatment "made things a lot better." Of those responding who had received longer treatment, 36 percent claimed that treatment "made things a lot better." Therefore, psychological treatment lasting more than 6 months is more effective than shorter-term treatment.
A consumer magazine surveyed people who had sought a psychologist's help with a personal problem. Of those responding who had received treatment for 6 months or less, 20 percent claimed that treatment "made things a lot better." Of those responding who had received longer treatment, 36 percent claimed that treatment "made things a lot better." Therefore, psychological treatment lasting more than 6 months is more effective than shorter-term treatment.
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.
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.
Patients who feel they are doing well in treatment tend to remain in treatment, while those who are doing poorly tend to quit earlier.
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.
Many psychologists encourage their patients to receive treatment for longer than 6 months.
Explanations
This argument concludes that psychological treatment lasting longer than six months is more effective than shorter-term treatment.
Why? Because less-than-six-month respondents reported success 20% of the time whereas more-than-six-month respondents reported success 36% of the time.
My first reaction was what if this is just a placebo effect?
For example, I don't go to therapy, but that doesn't mean it would be helpful if I did. Similarly, if I did go to therapy, and I felt like it was helping, that doesn't necessarily mean that it's helping. I could just feel like it's helping. What if these survey respondents are experiencing a placebo effect that's the real cause of them sticking with the therapy long-term? That's my prediction.
Let's see.
Nah. This doesn't matter because we have nothing to compare it to. The only thing we know about both groups is the rate at which respondents claim treatment is helping them.
Nope. Such a trap. All this tells me is that the sample size of the longer-than-six-months folks is necessarily larger than the less-than-six-months sample. Just because we have a bigger sample and more overall people reporting that therapy's working for them doesn't mean therapy's actually working for them.
Bingo, just what we predicted. This means the sample is biased in two directions—the number of people reporting good things goes up and the number of people who quit also goes up. Moreover, this points to the placebo effect: people feel like they're doing better, so they stick with it and report good things. That doesn't mean it's actually working.
Nah. This might explain why reported success rates were relatively low, but this doesn't help me understand whether attending treatment for more than six months is more effective than the alternative.
No way. This is a "cool story, bro" answer. I'm sure this is true because therapists are incentivized to do this, but it doesn't affect the conclusion whatsoever.
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