One more thing, I said they're not independent, so we have to talk about the covariance between the returns.

还有，我说过它们不是相互独立的，因此我们还需要讨论两个收益率的协方差。

耶鲁公开课 - 金融市场课程节选

You take all the risky assets ... and you analyze them first to get their-- you have to do a statistical analysis to get their expected returns, their variances, and their covariances.

你需要对所有的风险资产进行分析,首先要得到它们的-,你必须要做一个统计分析,算出它们的预期收益率，方差，和它们的协方差。

耶鲁公开课 - 金融市场课程节选