请教一道GWD的逻辑题，做志愿者长寿的那道，麻烦NN

Cherliuiking

When people engage in activities that help others, their brain releases endorphins, the brain’s natural opiates, which induce in people a feeling of well-being. It has been suggested that regular release of endorphins increases people’s longevity. And a statistic on adults who regularly engage in volunteer work helping others shows that they live longer, on average, than adults who do not volunteer. However, that statistic would be what we would expect even if volunteering does not boost longevity, because    .

A.    in the communities studied, women were much more likely to do regular volunteer work than men were, and women tend to live longer than men do.
B.    the number of young adults who do regular volunteer work is on the increase
C.    ! the feelings of well-being induced by endorphins can, at least for a time, mask the symptoms of various conditions and diseases, provided the symptoms are mild.
D.    it is rare for a person to keep up a regular schedule of volunteer work throughout his or her life.
E.    Some people find that keeping a commitment to do regular volunteer work becomes a source of stress in their lives.
为什么选A呢？题中不是说了即使是做志愿者不会

sandywood

这道题选A， 是新PREP里的题。

题目是说这个统计的结果正如我们所预料的，即使志愿工作并不促进长寿，因为----大多数是女人做志愿者工作，而女人往往比男人长寿。

prayer

答案是A，没错的。统计样本的问题。引用Manhattan的Ron的解释给你看。

basically, here's what going on here.

* the passage has noticed a CORRELATION between volunteerism and long life.

* the passage is questioning the notion that volunteerism CAUSES longer life.

takeaway:
in any passage that takes CORRELATION and concludes CAUSATION, that connection can be destroyed if either:
(a) the causation actually runs the other way around (i.e., the passage concludes that X causes Y, but in actuality Y causes X);
(b) the two correlated things are both results of some third, not considered, confounding factor.

as an example of (b):
there is a strong correlation between the # of churches and the # of murders in american cities: the more churches, the more murders.
however, there is no causation at work here (churches don't cause murders, and murders don't cause the building of churches), because both of these factors are caused by a third factor: the SIZE of the city. (IE larger cities have both more churches and more murders.)

--

in this case, the sex of the volunteers is the "third, not considered, thing" that destroys the hypothesis of causal connection between volunteerism and long life.

hope that helps.