Section 3, Question 15 of the June 2007 LSAT presents this stinker of an argument: 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.
Ideally, you'll be able to poke holes in this one before proceeding to the answer choices. This isn't the only way to do the test, but it's the best one. Can you tell me why the above argument is bullshit?
Ask yourself: What's the evidence? What's the conclusion? Does it add up?
I think the evidence basically boils down to "those who received treatment for longer than 6 months were more likely to report that the treatment helped than those who received treatment for 6 months or less." The conclusion is "psychological treatment lasting more than 6 months is more effective than shorter-term treatment."
It's not unreasonable, but it's not proven either. Imagine if the argument had said "people who buy $300 bottles of wine are more likely to report that the wine they drink is excellent than are people who buy Two Buck Chuck, therefore wine that is more expensive is clearly better wine." Wouldn't you argue with that? I'd say something like "well of course douches who waste $300 on a bottle of wine are more likely to say the wine they drink is excellent. If they didn't say that, why the hell would they buy the wine? That doesn't mean they are right though." In other words, it's likely that people who think $300 wine is good are those who will buy it. This doesn't prove it's actually good though.
Same deal with the argument presented in question 15. It's likely that people who think a psychologist is helping them tend to stay in treatment longer. So when they report their own results, it appears as if people who stay in treatment longer get better results. But actually, all that might be happening is selection bias.
The question asks,
Which one of the following, if true, most seriously weakens the argument?
Great, because I've already been arguing. I'm not 100% certain that my hypothesis above will be related to the correct answer, but it certainly could be used as a weapon. Something like "people who think therapy is working are more likely to stay in therapy for a longer period" would be a pretty devastating weakener. Time to look at the answer choices.
(A) Of the respondents who had received treatment for longer than 6 months, 10 percent said that treatment made things worse.
This would neither strengthen nor weaken the argument, because it doesn't provide any comparison with the group who received treatment for less than 6 months. If only 5 percent of those who received treatment for less than 6 months said the treatment made them feel worse, then yes this would be a weakener. But if 50 percent of the shorter-term patients said treatment made them feel worse, then this answer would actually strengthen the argument. So this one is out.
(B) 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.
Tricky, but no. The raw number of responses isn't at issue at here. The only thing that's at issue is the results of the survey. Why did those who had longer treatment report better results? Was it because of the quality of the treatment, or was it because of something else?
(C) Patients who feel they are doing well in treatment tend to remain in treatment, while those who are doing poorly tend to quit earlier.
Bingo. This matches our prediction, above. If this is true, then the survey isn't proving that longer treatment is better, just that people who feel they are getting benefit out of treatment tend to stay in treatment longer. I'm 99% certain this will be our answer, but I'll always read D and E just in case.
(D) 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.
Almost the same explanation as B. The argument was trying to explain a qualitative difference in the responses from two different groups of patients. The quantity of responses doesn't help with that.
(E) Many psychologists encourage their patients to receive treatment for longer than 6 months.
So what? How does this change the given argument?
Our answer is C, because if C is true it would seriously interfere with the conclusion that the argument attempted to make.