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，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?

以这个人口据为基础再用标准公式，你觉得变量是少？

Remember, z-score is just how many standard deviations you are away from the mean.

请记住，z-score 就是您与平均值之间的标准偏。

If you personalize, then you get two standard deviations, more effective learning.

果你进行个性化学习，那么学习效果会提升两个标准。

Well, the scale of the effect size is based on standard deviations.

效应规模的量级是基于标准的。

I'm not that far out of two standard deviations down on Apple.

我在苹果公司的表现没有到两个标准那么远。

And the VIX were close to three standard deviations above the long-term median.

而VIX指接近长期中位上方的三个标准。

They are a couple standard deviation outliers.

他们是几个标准的异常值。

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。

Do you know how to calculate the standard deviation ?

你知道何计算标准吗？

The Levey-Jennings chart uses the calculated standard deviation (for example, from STDEV in Excel).

Levey-Jennings 图表使用计算出的标准（例，来自 Excel 中的 STDEV）。

Then use the range chart to estimate the process standard deviation.

然后使用极图来估计过程标准。

Let's say 2.79 is the standard deviation.

假设2.79是标准偏。

What if we got two standard deviations more conscientious?

果我们得到两个更认真的标准呢？

And the standard deviation is 0.5.

标准是0.5。

The mean weight of the sample is 112 grams with a 40 gram sample standard deviation.

样本的平均重量为112克，样本标准为40克。

We don't know what that mean weight is, and it also has a population standard deviation.

我们不知道那个平均重量是少，它也有一个总体标准。

We just need to figure out how many standard deviations is 5 from the mean?

我们只需要计算出 5 与均值的标准是少？

A little more challenging but very important is to  describe how the standard deviation changes.

稍微有点挑战性但非常重要的是描述标准是何变化的。