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

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