.. 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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If they tend to move together, when x is high and y is high together at the same time, then the covariance will tend to be a positive number.

如果x和y同向变动,当x值和y值同时都很大,协方差的结果将会是一个正值

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