One person might be a little low one day, another person might be high, a lot of people might-- you might happen to have captured them on an average day, but overall it averages out, so you get a representative sample.

一个人可能某一天少吃些,另一个人可能多吃些,很多人都会这样,你可能正好得出人们,平均每天的摄入量,但把它的整体平均一下,就得到有代表性的结果

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

but, uh, some days it's more, some days it's less, sometimes I don't study at all.

不过，时间不固定，有时候多，有时候少，有些时候我一天都不学习。

MIT的时尚品味 - SpeakingMax英语口语达人