Because usually it doesn't work. And so one of the things that I think is very important is to always begin by testing each unit.

因此我认为非常重要的一件事情,就是开始测试的时候先对,每个独立单元进行测试。

麻省理工公开课 - 计算机科学及编程导论课程节选

The way you would go about it, if you're a portfolio manager, is you have to come up with estimates of the inputs to these formulas-- that means the expected returns, the standard deviations, and the covariances.

你所要做的，如果你是一个资产经理，你要做的事情就是,对公式里面的一些参数进行估计-,那些参数包括预期收益，标准差，和协方差。

耶鲁公开课 - 金融市场课程节选