You're taking 12 samples, taking its mean.

您正在采集 12 个样本，取其平均值。

Police say the samples taking from the school in Bihar contain what they described as very toxic levels of organic phosphorus compound.

警方称在比哈尔这所学校提取的样本中含有高浓度的剧毒有机磷化合物。

So if I know the standard deviation, and I know n is going to change depending on how many samples I'm taking every time I do a sample mean.

因此， 如果我知道标准偏差，并且我知道 n 将根据我每次做样本均值时采集的样本数量而变化。