The 2 sigma comes from two standard deviation, sigma, the symbol for standard deviation.

2 sigma 来自两个均方差，sigma 是均方差的符号。

Readers have to wait until page 65 before reaching the first serious concept, standard deviation, which feels too late.

读者得等上65页才能接触到第一个严肃的统计学概念——标准差，让人感觉进度太慢。

The critical variable was the standard deviation of the means divided by the mean of the standard deviations.

关键变量是均值的标准差除以标准差的均值。

It has a standard deviation of 0.7 liters or 0.7 liters.

它的标准偏差为 0.7 升或 0.7 升。

So the standard deviation-- maybe I'll draw it this way.

所以标准偏差——也许我会这样画。

Raymond, you were the one who scored one standard deviation higher than Debra.

雷蒙德，你的成绩应该比黛布拉高一个等级。

So based on the data given for this population, and using the standard deviation formula, what do you think this variable is?

以这个人口数据为基础再用标准差公式，你觉得变量是多少？

And then one standard deviation is going to be 0.7 liters away.

然后一个标准偏差将是 0.7 升。

That right there is the standard deviation to the right, that's the standard deviation to the left.

右边是右边的标准差，左边是标准差。

That we are less than 2.02 standard deviations above the mean.

我们比平均值高出不到 2.02 个标准差。