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。

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？

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。

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。

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。

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。

The standard deviation-- actually maybe put it a better way.

标准差——实际上也许可以用更好的方式表达。

And we know that the standard deviation is equal to-- I'll write the 0 in front, 0.7 liters.

我们知道标准偏差等于——我会在前面写上 0，即 0.7 升。

We know what the standard deviation of the population is.

我们知道总体的标准差是多少。

That's going to be the standard deviation of this.

这将是这个的标准偏差。

It's going to have a lower standard deviation.

它将具有较低的标准偏差。

This is actually going to be a normal distribution regardless of-- this one just has a well-defined standard deviation mean.

这实际上将是一个正态分布，无论如何 - 这个只是有一个明确定义的标准偏差平均值。

The standard deviation of this distribution is 0.099.

此分布的标准偏差为 0.099。

The standard deviation is almost a tenth, so it's going to be a much narrower distribution.

标准差几乎是十分之一，所以它的分布要窄得多。

But anyway, so we need to figure out the probability that the sample mean will be more than 2.02 standard deviations above the mean.

但无论如何，我们需要计算样本均值高于均值 2. 02 个标准差的概率。

And if you wanted the standard deviation of this distribution right here, you just take the square root of both sides.

如果你想要这个分布的标准偏差就在这里，你只需取两边的平方根。