And then the population standard deviation.

然后是总体标准差。

The population standard deviation assuming our null hypothesis.

假设我们的原假设的总体标准差。

And we always have to put a little confidence there, because remember, we didn't actually know the population standard deviations, or the population variances.

而且我们总是必须在那里放一点信心， 因为请记住，我们实际上并不知道总体标准偏差或总体方差。

If you will have more than 30 samples, if your sample size is more than 30, your sample standard deviation is going to be a good approximator for your population standard deviation.

如果您有超过 30 个样本，如果您的样本量超过 30，则您的样本标准差将是总体标准差的一个很好的近似值。

So the standard deviation of our sampling distribution is going to be-- and we'll put a little hat over it to show that we approximated it with-- we approximated the population standard deviation with the sample standard deviation.

所以我们的抽样分布的标准偏差将是——我们会在它上面戴一个小帽子来表明我们用它来近似——我们用样本标准偏差来近似总体标准偏差。