If you want to find the mean value of five different numbers, you would add those numbers together and divide by five.

如果你想找到五个不同数字的平均值，你可以将这些数字加在一起并除以五。

Well, if we take this whole sum and we divide it by n terms, this is going to be the mean value for x times y.

好吧，如果我们把这个总和除以 n 项， 这将是 x 乘以 y 的平均值。

If we wanted to know the expected, or if we talked about the expected value of this random variable x, that is the same thing as the mean value of this random variable x.

如果我们想知道期望值，或者如果我们谈论这个随机变量 x 的期望值， 那与这个随机变量 x 的平均值是一回事。