So it's the standard deviation of the distribution of the mean of x1 minus the sample mean of x2.

所以它是 x1 的均值分布的标准差减去 x2 的样本均值。

All of these things I just mentioned, these all just mean the standard deviation of the sampling distribution of the sample mean.

我刚才提到的所有这些东西，这些都只是意味着样本均值的抽样分布的标准偏差。