This formula will often underestimate the actual population variance.

该公式通常会低估实际的总体方差。

This is the actual population distribution, not the sampling distribution of the sample mean.

这是实际的总体分布，而不是样本均值的抽样分布。

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。