That's got the lowest possible standard deviation of expected return and that's 25% stocks and 75% bonds with this sample period.

这个组合预期回报的标准差最小,在这一点上，投资组合,由25%的股票和75%的债券构成。

耶鲁公开课 - 金融市场课程节选

It shows the standard deviation of the return on the portfolio as a function of the expected return on the portfolio.

它是投资组合的收益标准差,关于预期收益率的函数图像。

耶鲁公开课 - 金融市场课程节选

But if I would confine myself just to stocks and bonds, then I would get a much higher standard deviation.

但若组合里只有股票和债券，我的标准差会高得多。

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.. You want to get it-- if you keep adding assets, you can do better and better on your portfolio standard deviation.

你想得到-,如果不断增加资产,组合的标准差就会越来越小。

耶鲁公开课 - 金融市场课程节选

You could always find a portfolio that had a higher expected return for the same standard deviation.

你总是可以找到一个投资组合,具有较高的预期回报,而标准差不变。

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Because the square root of 10,000 is 100, whatever the standard deviation of the portfolio is, you would divide it by 100 and it would become really small.

因为一万的平方根是一百，无论这个投资组合的标准差是多大，当除以100后就都变得很小很小了。

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Over this time period, that portfolio had an expected return of something like a little over 9% and it had a standard deviation of a little over 9%.

在这个时间段，这个投资组合的预期收益率是,9%多一点%,标准差是9%多一点。

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So, for example, at an annual expected return of 12% if I have a portfolio of stocks, bonds, and oil I can get a standard deviation of something like 8% on my portfolio.

例如，在年预期收益12%的情况下%,我有股票，债券和石油的投资组合,在这个组合里,我的投资组合可以取到8%的标准差。

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Then, once we did that we could plug that into the formula that I gave you last time and get the standard deviation of the portfolio and the expected return on the portfolio.

再将估算出的数值代入到,上节课给你们的公式中,就能得到资产投资组合的标准差,和该投资组合的预期收益率

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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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So, the optimal thing to do if you live in a world like this n is to get n as large possible and you can reduce the standard deviation of the portfolio very much and there's no cost in terms of expected return.

如果现实中也这样简单的话,那么你就尽量增大,这样就能让投资组合的标准差,就会大大降低,从预期收益率的角度来看,这样做的成本是零。

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