Another important concept in probability theory that we will use a lot is expected value, the mean, or average-- those are all roughly interchangeable concepts.

概率论中另外一个常用的重要的概念是,期望值或者也叫均值,这两个概念可以互换

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I mean, the average, you know, the sort of typical workdays, 8 or 9 hours.

我是说，平均而言，正常的工作日，八九个小时。

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People also call that the mean or the average.

也可以叫做平均值

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We have expected value, mean or average.

我们可以用期望值,或者是平均值

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