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

2 sigma 来自两均方差，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?

以这人口数据为基础再用标准差公式，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差数。

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

如果你进行性化学习，那么学习果会提升两标准差。

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

模的量级是基于标准差的。

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

我在苹果公司的表现没有差到两标准差那么远。

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

而VIX指数接近长期中位数上方的三标准差。

They are a couple standard deviation outliers.

他们是几标准差的异常值。

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

雷蒙德，你的成绩该比黛布拉高等级。

Do you know how to calculate the standard deviation ?

你知道如何计算标准差吗？

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差（例如，来自 Excel 中的 STDEV）。

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

然后使用极差图来估计过程标准差。

Let's say 2.79 is the standard deviation.

假设2.79是标准偏差。

What if we got two standard deviations more conscientious?

如果我们得到两更认真的标准差呢？

And the standard deviation is 0.5.

标准差是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，样本标准差为40克。

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

我们不知道那平均重量是少，它也有总体标准差。

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

我们只需要计算出 5 与均值的标准差是少？

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差是如何变化的。