This formula will often underestimate the actual population variance.

该公式通常会低估实际的总体方差。

And then this sample variance, calculated this way, will actually underestimate the actual population variance, because they're always going to be closer to their own mean than they are to the population mean.

然后，以这种方式计算出的样本方差实际上会低估实际总体方差，因为它们总是更接近自己的均值，而不是总体均值。

So the actual variance of the sample, if you had actually known the mean-- I know this is all a little confusing-- if you had actually known the mean, you would've said, oh, wow.

所以样本的实际方差，如果你真的知道平均值——我知道这有点令人困惑——如果你真的知道平均值， 你会说，哦，哇。