两道费费逻辑

onedayling

第92题
Baking for winter holidays is a tradition that may have a sound medical basis. In midwinter, when days are short, many people suffer from a specific type of seasonal depression caused by lack of sunlight. Carbohydrates, both sugars and starches, boost the brain’s levels of serotonin, a neurotransmitter that improves the mood. In this respect, carbohydrates act on the brain in the same way as some antidepressants. Thus, eating holiday cookies may provide an effective form of self-prescribed medication.
Which one of the following can be properly inferred from the passage?
(D) Some antidepressants act by changing the brain’s level of serotonin.
(E) Raising the level of neurotransmitters in the brain effectively relieves depression.

Why is E incorrect?

第94题
When 100 people who have not used cocaine are tested for cocaine use, on average only 5 will test positive. By contrast, of every 100 people who have used cocaine 99 will test positive. Thus, when a randomly chosen group of people is tested for cocaine use, the vast people is tested for cocaine use, the vast majority of those who test positive will be people who have used cocaine.
A reasoning error in the argument is that the argument
(C) fails to take into account what proportion of the population have used cocaine
(D) ignores the fact that some cocaine users do not test positive
不明白题干的意思,尤其最后一句,the vast people is...,the vast...will be...都是完整的句子,中间没有连词,若是主从句,孰为主句?

iwvers

92.从这句话, boost the brain’s levels of serotonin, a neurotransmitter that

improves the mood, 得知, 只是serotonin有抗忧郁的作用, 而不是所有的neurotransmitte.

94. 可以举几个数字来说明一下这道题
例如, 假设测试的人数是1000人,
        假如该1000人是没使用咖啡因的, 根据文章, 得知可能有5%即50人呈阳性却没使用咖

啡因;
        假如该1000人中有5%确实使用了咖啡因, 根据题意, 使用了咖啡因的99%会被检出,

则约有50人呈阳性的人使用了咖啡因. 
       因此, 如果没告诉测试人群中使用咖啡因的比例, 测试结果大大不同. 文中结论说呈

阳性则使用了咖啡因是不正确的.
      the vast people is...,the vast...will be  意思是测试的人越多, 越......, the

more ...the more 意思.

onedayling

 豁然开朗,多谢!

xingzixin

" The argument fails to consider the composition of population and makes an

unwarranted assumption that among a random group of people, non-users are less

than 99/5 of users. X: non-users Y: users. 5%X < 99%Y è x<99/5Y. "

以上是FEFEI详解里的解释, x<99/5Y只能够保证people who has used cocaine是majority of

those who test positive,即99%Y/5%X+99%Y>1/2

但是如果the vast....the vast...是the more...the more...的意思,是不是意味着:X+Y越大

,99%Y/5%X+99%Y的比值就越大? 那即使给出X<99/5Y,题目中的结论也不能成立啊.或者应该把

这个比例要求看成是assumption?,即必要非充分条件?

这种error题需不需要充分性啊?