SDCAR2010【逻辑入门】（八）Assumptions

米样

这一部分真是我的软肋啊，看这篇帖子都比较吃力。。。

dualtunnal

牛牛，sufficient和necessary分不清啊，牛牛给的例子看得很清楚，不过出在题目里面就分不清啦，感觉justify the conclusion 和 rely on the assumption差不多啊，求解答~

glendasc

For question No.2
2. A researcher discovered that people who have low levels of immune-system activity tend to score much lower on tests of mental health than do people with normal or high immune-system activity. The researcher concluded from this experiment that the immune system protects against mental illness as well as against physical disease.
The researcher's conclusion depends on which of the following assumptions?
(A) High immune-system activity protects against mental illness better than normal immune system activity does.
(B) Mental illness is similar to physical disease in its effects on body systems.
(C) People with high immune-system activity cannot develop mental illness.
(D) Mental illness does not cause people's immune system activity to decrease.
(E) Psychological treatment of mental illness is not as effective as is medical treatment.

But if you negate C. people with high immune-system activity CAN develop mental illness. If that is true, then the conclusion that the immune system protects against mental illness is wrong. So why choose D but not c?

sdcar2010

For question No.2
2. A researcher discovered that people who have low levels of immune-system activity tend to score much lower on tests of mental health than do people with normal or high immune-system activity. The researcher concluded from this experiment that the immune system protects against mental illness as well as against physical disease.
The researcher's conclusion depends on which of the following assumptions?
(A) High immune-system activity protects against mental illness better than normal immune system activity does.
(B) Mental illness is similar to physical disease in its effects on body systems.
(C) People with high immune-system activity cannot develop mental illness.
(D) Mental illness does not cause people's immune system activity to decrease.
(E) Psychological treatment of mental illness is not as effective as is medical treatment.

But if you negate C. people with high immune-system activity CAN develop mental illness. If that is true, then the conclusion that the immune system protects against mental illness is wrong. So why choose D but not c?

-- by 会员 glendasc (2011/7/15 23:25:01)

If you negate C), the conclusion still holds since the conclusion is "the immune system PROTECTs against mental illness,", which means people with high immune system have some protection but that protection is not bullet-proof. So people with high immune system could become mentally unstable, but less likely than those who have low immune system.

sdcar2010

牛牛，sufficient和necessary分不清啊，牛牛给的例子看得很清楚，不过出在题目里面就分不清啦，感觉justify the conclusion 和 rely on the assumption差不多啊，求解答~

-- by 会员 dualtunnal (2011/7/15 22:15:12)

justify the conclusion: sufficient assumption

rely on the assumption: necessary assumption

srosalita

For question No.2
2. A researcher discovered that people who have low levels of immune-system activity tend to score much lower on tests of mental health than do people with normal or high immune-system activity. The researcher concluded from this experiment that the immune system protects against mental illness as well as against physical disease.
The researcher's conclusion depends on which of the following assumptions?
(A) High immune-system activity protects against mental illness better than normal immune system activity does.
(B) Mental illness is similar to physical disease in its effects on body systems.
(C) People with high immune-system activity cannot develop mental illness.
(D) Mental illness does not cause people's immune system activity to decrease.
(E) Psychological treatment of mental illness is not as effective as is medical treatment.

But if you negate C. people with high immune-system activity CAN develop mental illness. If that is true, then the conclusion that the immune system protects against mental illness is wrong. So why choose D but not c?

-- by 会员 glendasc (2011/7/15 23:25:01)

If you negate C), the conclusion still holds since the conclusion is "the immune system PROTECTs against mental illness,", which means people with high immune system have some protection but that protection is not bullet-proof. So people with high immune system could become mentally unstable, but less likely than those who have low immune system.

-- by 会员 sdcar2010 (2011/7/16 0:02:26)

Dear scdcar2010,
Can you tell me how to negate this sentence "children who don't spend all of their after-school hours playing computer games spend at least some of that time talking with other people." Can i translate it into： children who don't spend all of their after-school hours playing computer games spend most of that time talking with other people?
Besides, how to use a negated sentence to undermine the conclusion, is it need to corporate the existed premises to undermine it?

sdcar2010

children who don't spend all of their after-school hours playing computer games spend NONE of that time talking with other people.

sdcar2010

children who don't spend all of their after-school hours playing computer games DO NOT spend at least some of that time talking with other people

rongyang114

sdcar，可以转帖吗？更多人可以学习到~

AlohaDJ

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