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

2 sigma 来自两个均方，sigma 是均方号。

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统计学概念——，让人感觉进度太慢。

1, 2, 3 standard deviations below the mean.

低于平均值 1、2、3 个。

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

关键变量是均值除以均值。

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

它偏为 0.7 升或 0.7 升。

And we'll talk-- and we'll move into the standard deviation.

我们将讨论——我们将进入。

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

所以偏——也许我会这样画。

So this result right here is 3 standard deviations away from the mean.

所以这里结果与平均值相 3 个。

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

雷蒙德，你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公式，你觉得变量是多少？

If I did 1 standard deviation, 2 standard deviations, 3 standard deviations-- that's in the positive direction.

如果我做了 1 个、2 个、3 个——那就是正方向。

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

然后一个偏将是 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，左边是。

So we go down another standard deviation in that direction and another standard deviation above the mean.

所以我们在那个方向上再下降一个，在平均值之上再下降一个。

Now if we're talking about two standard deviations around the mean-- so if we go down another standard deviation.

现在，如果我们谈论均值附近两个——那么如果我们再下降一个。

So above three standard deviations below the mean, and below three standard deviations above the mean.

所以高于均值三个，低于均值三个。

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。

So they gave us the mean and the standard deviation.

所以他们给了我们平均值和。

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

我们知道偏等于——我会在前面写上 0，即 0.7 升。

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

——实际上也许可以用更好方式表达。