And the other thing you can do is take self reports like the ones you're doing, hopefully do enough of them, and a random enough sample of the population, that you can extrapolate from that sample to the whole population, and try to estimate what people are eating in that way.

还有其他可以做的,比如大家正在做的这种个体调查,希望能把它做的充分些,如果有充足的随机样本,就可以从样本推断出,整个总体,从而推断哪类人有这样的饮食习惯

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

This is very important,which is why I am doing it: "If we want to know how fast a human being can run, then it is no use to average out the speed of a "good sample" of the population; it is far better to collect Olympic gold medal winners and see how well they can do.

这话非常重要，是我作这个研究的原因：,“如果想知道人类最快能跑多快，那从好的样本中测出平均数是“,没用的;,而应该收集田径类奥运冠军的信息,看他们能跑多快。

哈佛公开课 - 幸福课课程节选

In a poll, why must there be a clear and accurate link between sample and population?

CNN: The Polls

These analyses are based on the assumption that the animals collected represent a randomly selected and thus representative sample of the population.

ECONOMIST: Animal personalities

The new results are the first from an ongoing study intended to assess mental health in a representative population sample, balanced for demographics and including people who returned home and those who remain dispersed around the country.

NPR: Mental Issues Surge, Suicide Rates Flat Post-Katrina