There's no correlation between them ... and that means that the variance-- and I want to talk about equally-weighted portfolio.

它们之间没有相关性,也就是说。。。方差-,我想讲一下,权重相等的投资组合。

耶鲁公开课 - 金融市场课程节选

If you're comparing two portfolios with the same expected return, then you want the one with the lower variance.

比较两个有相同预期收益率的投资组合时，你会选择方差小的那一个。

耶鲁公开课 - 金融市场课程节选

What we did--the core theoretical framework that we had-- was the mean variance theory, which led us to the capital asset pricing model.

我们讲到了投资组合多元化的核心理论框架,即均值-方差模型,之后又讲到了资本资产定价模型

耶鲁公开课 - 金融市场课程节选

In fact, I have it--suppose we have three assets and we want to compute the efficient portfolio frontier, the mean and variance of the portfolio.

事实上，假如我们拥有三种资产,我们想计算有效边界，及投资组合的均值和方差。

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.. If you can find assets that all have-- that are all independent of each other, you can reduce the variance of the portfolio very far.

如果你能找到这样的一些资产-,一些相互独立的资产，就能很大程度上缩小这个投资组合的方差。

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There's a very important principle that finally comes out here, it is that you always want to reduce the variance of your portfolio as much as you can.

现在这里有一个非常重要的原则，即你总是想要降低你投资组合的方差,降得越低越好。

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But ultimately, everyone agrees I-- that's the premise here, that for the-- if you're comparing two portfolios with the same variance, then you want the one with the higher expected return.

但归根结底大家都会同意这一点-,这是一个前提-,当你比较两个有相同方差的投资组合时，你会选择预期收益率高的那一个。

耶鲁公开课 - 金融市场课程节选

But, in between, if some other number, it'll be some blend of the--mean and variance of--the portfolio will be some blend of the mean and variance of the two assets.

但如果是在0和1之间的其他数值，这个投资组合的均值和方差将会是,两项资产各自的均值和方差的综合结果。

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Now, underlying our theory is the idea that we measure the outcome of your investment in your portfolio by the mean of the return on the portfolio and the variance of the return on the portfolio.

而理论的基础是,我们通过计算,组合收益率的均值，和组合收益率的方差,来衡量一个投资组合的优劣。

耶鲁公开课 - 金融市场课程节选

What we want to do now is compute the mean and variance of the portfolio-- or the mean and standard deviation, since standard deviation is the square root of the variance-- for different combinations of the portfolios.

我们现在要做的是,计算这个投资组合的均值和方差-,或者均值和标准差，因为标准差的平方就等于方差-,这对任何投资组合都是一样的。

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x1 The portfolio mean and variance will depend on x1 x1=1 in the way that if you put--if you made x1 = 1, it would be asset 1 x1=0 and if you made x1 = 0, then it would be the same as asset 2 returns.

投资组合的均值和方差取决于1,如果你令，投资组合的均值方差就与第一项资产相等1,如果你令，那么它们就会与第二项资产的参数相等。

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So, the higher the covariance is, generally, the higher--you can see from here-- 2 of the portfolio.

所以总的来说，你可以从这里看出，协方差越大-,投资组合的σ2越高，the，higher，the，σ

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