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June 2007, Logical Reasoning 2, Question 15


Question 15, when a question asks you for something that weakens the argument, you're dealing with a weakened question, no big surprise there. On a weakened question, your job is to attack the argument's assumptions. Of course, you can't attack the assumptions until you know what they are. And you won't know what they are until you break the argument down, you digest it, figure out its conclusion and it's evidence.

Here the conclusion is flagged without helpful conclusory keyword therefore. Therefore psychological treatment lasting more than six months is more effective than shorter-term treatment. To prove this conclusion, they basically give us one piece of evidence. There was a survey. The first sentence tells you that there was a survey, the second sentence tells you about the survey.

The survey was basically a comparison between two different groups. The first group was people who had received treatment for six months or les. And only 20% of them said that the treatment they'd received made things a lot better. The second part was people who'd been surveyed after six months, and 36% of them said the treatment made things better.

So on the basis of that, they say, thus, treatment that lasts for longer than six months is more effective than shorter term treatment. Arguments involving surveys have very similar assumptions. The assumptions are essentially first, that the survey is representative of people who need therapy, that the people in this weren't special in some way that would throw the results off.

And second, that there was no source of bias that snuck into the survey. The way they selected the people, the way that they asked the questions, that nothing changed the way that they would answer, tilting them towards being more satisfied later on. So the correct answer will attack one of those assumptions, let's see what we have to deal with.

Answer choice A, answer choice A might seem like it hurts the argument. Because it does say that 10% of people said the treatment made things worse after six months. But actually, that's something that's already possible within the information we already have. The argument said that only 36% of people thought that it made things a lot better.

So that leaves 64% who could think all sorts of things. All this answer choice does is give us an exact number who said it made things a lot worse, 10%. That doesn't change that the number is still going up from 20 to 36%. So even though some people are unhappy, this doesn't disprove the idea that the longer treatment is helping more people.

On to answer choice B. Now, this one might seem like it's the answer. Because it does give us something that's strange about the people who were receiving treatment for more than six months. They were more likely to respond to surveys. But that doesn't mean that they're lying.

And that doesn't mean that they're more likely to say they're happy. They're just more likely to respond. So this is a difference between the people in the pre six month and post six month category. But not a difference that would change the way that we feel about what they said. So answer choice B, it's not the answer.

Go to answer choice C. Now, this is going to end up being our answer because it gives us a source of bias in the way that the survey was constructed. If patients who feel that they're doing well in treatment tend to remain in treatment, while those who are doing poorly tend to quit earlier. The longer the treatment, the higher the percentage of happy people become.

Not because more people are becoming happy, but because the unhappy people are dropping out. So the survey is suspect, the argument has been weakened. And I'll take a courtesy glance at the answer choices that are left just to see why they're wrong. Answer choice D, this may seem a lot like answer choice C.

Patients who were dissatisfied with the treatment were more likely, but it doesn't say they're more likely to drop out. It's just they're more likely to feel the need to express their feelings. So this would actually help the argument, because the people who were upset would be more likely to say something. And yet, when we look at the survey results, more people were happy after six months than before six months.

So answer choice E. Well, what psychologists encourage is, ironically, not a part of this argument at all. They're not discussing what psychologists recommend, just what would be effective. So answer choice E is not the answer. The answer is C.

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